Merge pull request #6 from wcharczuk/v2.0-devel

moving over to v2.0

.travis.yml

@@ -6,8 +6,8 @@ go:
 sudo: false
 
 before_script:
-  - go build -i ./...
+  - go get -u github.com/blendlabs/go-assert
+  - go get ./...
 
 script:
-  - go test
+  - go test ./...
-  - go test ./drawing/

Makefile

@@ -0,0 +1,9 @@
+all: test
+
+test:
+	@go test ./...
+
+cover:
+	@go test -short -covermode=set -coverprofile=profile.cov
+	@go tool cover -html=profile.cov
+	@rm profile.cov

README.md

@@ -31,13 +31,19 @@ Two axis:
 
 ![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/two_axis.png)
 
-Simple Moving Average:
+# Other Chart Types
 
-![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/ma_goog_ltm.png)
+Pie Chart:
 
-Bollinger Bounds:
+![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/pie_chart.png)
 
-![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/spy_ltm_bbs.png)
+The code for this chart can be found in `examples/pie_chart/main.go`.
+
+Stacked Bar:
+
+![](https://raw.githubusercontent.com/wcharczuk/go-chart/master/images/stacked_bar.png)
+
+The code for this chart can be found in `examples/stacked_bar/main.go`.
 
 # Code Examples
 

annotation_series.go

@@ -2,18 +2,12 @@ package chart
 
 import "math"
 
-// Annotation is a label on the chart.
-type Annotation struct {
-	X, Y  float64
-	Label string
-}
-
 // AnnotationSeries is a series of labels on the chart.
 type AnnotationSeries struct {
 	Name        string
 	Style       Style
-	YAxis       YAxisType
+	YAxis       yAxisType
-	Annotations []Annotation
+	Annotations []Value2
 }
 
 // GetName returns the name of the time series.
@@ -27,10 +21,21 @@ func (as AnnotationSeries) GetStyle() Style {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (as AnnotationSeries) GetYAxis() YAxisType {
+func (as AnnotationSeries) GetYAxis() yAxisType {
 	return as.YAxis
 }
 
+func (as AnnotationSeries) annotationStyleDefaults(defaults Style) Style {
+	return Style{
+		Font:        defaults.Font,
+		FillColor:   DefaultAnnotationFillColor,
+		FontSize:    DefaultAnnotationFontSize,
+		StrokeColor: defaults.StrokeColor,
+		StrokeWidth: defaults.StrokeWidth,
+		Padding:     DefaultAnnotationPadding,
+	}
+}
+
 // Measure returns a bounds box of the series.
 func (as AnnotationSeries) Measure(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) Box {
 	box := Box{
@@ -40,22 +45,16 @@ func (as AnnotationSeries) Measure(r Renderer, canvasBox Box, xrange, yrange Ran
 		Bottom: 0,
 	}
 	if as.Style.IsZero() || as.Style.Show {
-		style := as.Style.WithDefaultsFrom(Style{
+		seriesStyle := as.Style.InheritFrom(as.annotationStyleDefaults(defaults))
-			Font:        defaults.Font,
-			FillColor:   DefaultAnnotationFillColor,
-			FontSize:    DefaultAnnotationFontSize,
-			StrokeColor: defaults.StrokeColor,
-			StrokeWidth: defaults.StrokeWidth,
-			Padding:     DefaultAnnotationPadding,
-		})
 		for _, a := range as.Annotations {
-			lx := canvasBox.Left + xrange.Translate(a.X)
+			style := a.Style.InheritFrom(seriesStyle)
-			ly := canvasBox.Bottom - yrange.Translate(a.Y)
+			lx := canvasBox.Left + xrange.Translate(a.XValue)
-			ab := MeasureAnnotation(r, canvasBox, style, lx, ly, a.Label)
+			ly := canvasBox.Bottom - yrange.Translate(a.YValue)
-			box.Top = MinInt(box.Top, ab.Top)
+			ab := Draw.MeasureAnnotation(r, canvasBox, style, lx, ly, a.Label)
-			box.Left = MinInt(box.Left, ab.Left)
+			box.Top = Math.MinInt(box.Top, ab.Top)
-			box.Right = MaxInt(box.Right, ab.Right)
+			box.Left = Math.MinInt(box.Left, ab.Left)
-			box.Bottom = MaxInt(box.Bottom, ab.Bottom)
+			box.Right = Math.MaxInt(box.Right, ab.Right)
+			box.Bottom = Math.MaxInt(box.Bottom, ab.Bottom)
 		}
 	}
 	return box
@@ -64,19 +63,12 @@ func (as AnnotationSeries) Measure(r Renderer, canvasBox Box, xrange, yrange Ran
 // Render draws the series.
 func (as AnnotationSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
 	if as.Style.IsZero() || as.Style.Show {
-		style := as.Style.WithDefaultsFrom(Style{
+		seriesStyle := as.Style.InheritFrom(as.annotationStyleDefaults(defaults))
-			Font:        defaults.Font,
-			FontColor:   DefaultTextColor,
-			FillColor:   DefaultAnnotationFillColor,
-			FontSize:    DefaultAnnotationFontSize,
-			StrokeColor: defaults.StrokeColor,
-			StrokeWidth: defaults.StrokeWidth,
-			Padding:     DefaultAnnotationPadding,
-		})
 		for _, a := range as.Annotations {
-			lx := canvasBox.Left + xrange.Translate(a.X)
+			style := a.Style.InheritFrom(seriesStyle)
-			ly := canvasBox.Bottom - yrange.Translate(a.Y)
+			lx := canvasBox.Left + xrange.Translate(a.XValue)
-			DrawAnnotation(r, canvasBox, style, lx, ly, a.Label)
+			ly := canvasBox.Bottom - yrange.Translate(a.YValue)
+			Draw.Annotation(r, canvasBox, style, lx, ly, a.Label)
 		}
 	}
 }

annotation_series_test.go

@@ -15,11 +15,11 @@ func TestAnnotationSeriesMeasure(t *testing.T) {
 		Style: Style{
 			Show: true,
 		},
-		Annotations: []Annotation{
+		Annotations: []Value2{
-			{X: 1.0, Y: 1.0, Label: "1.0"},
+			{XValue: 1.0, YValue: 1.0, Label: "1.0"},
-			{X: 2.0, Y: 2.0, Label: "2.0"},
+			{XValue: 2.0, YValue: 2.0, Label: "2.0"},
-			{X: 3.0, Y: 3.0, Label: "3.0"},
+			{XValue: 3.0, YValue: 3.0, Label: "3.0"},
-			{X: 4.0, Y: 4.0, Label: "4.0"},
+			{XValue: 4.0, YValue: 4.0, Label: "4.0"},
 		},
 	}
 
@@ -29,12 +29,12 @@ func TestAnnotationSeriesMeasure(t *testing.T) {
 	f, err := GetDefaultFont()
 	assert.Nil(err)
 
-	xrange := Range{
+	xrange := &ContinuousRange{
 		Min:    1.0,
 		Max:    4.0,
 		Domain: 100,
 	}
-	yrange := Range{
+	yrange := &ContinuousRange{
 		Min:    1.0,
 		Max:    4.0,
 		Domain: 100,
@@ -68,11 +68,11 @@ func TestAnnotationSeriesRender(t *testing.T) {
 			FillColor:   drawing.ColorWhite,
 			StrokeColor: drawing.ColorBlack,
 		},
-		Annotations: []Annotation{
+		Annotations: []Value2{
-			{X: 1.0, Y: 1.0, Label: "1.0"},
+			{XValue: 1.0, YValue: 1.0, Label: "1.0"},
-			{X: 2.0, Y: 2.0, Label: "2.0"},
+			{XValue: 2.0, YValue: 2.0, Label: "2.0"},
-			{X: 3.0, Y: 3.0, Label: "3.0"},
+			{XValue: 3.0, YValue: 3.0, Label: "3.0"},
-			{X: 4.0, Y: 4.0, Label: "4.0"},
+			{XValue: 4.0, YValue: 4.0, Label: "4.0"},
 		},
 	}
 
@@ -82,12 +82,12 @@ func TestAnnotationSeriesRender(t *testing.T) {
 	f, err := GetDefaultFont()
 	assert.Nil(err)
 
-	xrange := Range{
+	xrange := &ContinuousRange{
 		Min:    1.0,
 		Max:    4.0,
 		Domain: 100,
 	}
-	yrange := Range{
+	yrange := &ContinuousRange{
 		Min:    1.0,
 		Max:    4.0,
 		Domain: 100,

axis.go

@@ -1,20 +1,41 @@
 package chart
 
+type tickPosition int
+
+const (
+	// TickPositionUnset means to use the default tick position.
+	TickPositionUnset tickPosition = 0
+	// TickPositionBetweenTicks draws the labels for a tick between the previous and current tick.
+	TickPositionBetweenTicks tickPosition = 1
+	// TickPositionUnderTick draws the tick below the tick.
+	TickPositionUnderTick tickPosition = 2
+)
+
 // YAxisType is a type of y-axis; it can either be primary or secondary.
-type YAxisType int
+type yAxisType int
 
 const (
 	// YAxisPrimary is the primary axis.
-	YAxisPrimary YAxisType = 0
+	YAxisPrimary yAxisType = 0
 	// YAxisSecondary is the secondary axis.
-	YAxisSecondary YAxisType = 1
+	YAxisSecondary yAxisType = 1
 )
 
 // Axis is a chart feature detailing what values happen where.
 type Axis interface {
 	GetName() string
 	GetStyle() Style
-	GetTicks(r Renderer, ra Range, vf ValueFormatter) []Tick
+
+	GetTicks() []Tick
+	GenerateTicks(r Renderer, ra Range, vf ValueFormatter) []Tick
+
+	// GetGridLines returns the gridlines for the axis.
 	GetGridLines(ticks []Tick) []GridLine
-	Render(c *Chart, r Renderer, canvasBox Box, ra Range, ticks []Tick)
+
+	// Measure should return an absolute box for the axis.
+	// This is used when auto-fitting the canvas to the background.
+	Measure(r Renderer, canvasBox Box, ra Range, style Style, ticks []Tick) Box
+
+	// Render renders the axis.
+	Render(r Renderer, canvasBox Box, ra Range, style Style, ticks []Tick)
 }

bollinger_band_series.go

@@ -7,7 +7,7 @@ import "math"
 type BollingerBandsSeries struct {
 	Name  string
 	Style Style
-	YAxis YAxisType
+	YAxis yAxisType
 
 	Period      int
 	K           float64
@@ -27,7 +27,7 @@ func (bbs BollingerBandsSeries) GetStyle() Style {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (bbs BollingerBandsSeries) GetYAxis() YAxisType {
+func (bbs BollingerBandsSeries) GetYAxis() yAxisType {
 	return bbs.YAxis
 }
 
@@ -108,13 +108,13 @@ func (bbs *BollingerBandsSeries) GetBoundedLastValue() (x, y1, y2 float64) {
 
 // Render renders the series.
 func (bbs *BollingerBandsSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	s := bbs.Style.WithDefaultsFrom(defaults.WithDefaultsFrom(Style{
+	s := bbs.Style.InheritFrom(defaults.InheritFrom(Style{
 		StrokeWidth: 1.0,
 		StrokeColor: DefaultAxisColor.WithAlpha(64),
 		FillColor:   DefaultAxisColor.WithAlpha(32),
 	}))
 
-	DrawBoundedSeries(r, canvasBox, xrange, yrange, s, bbs, bbs.GetPeriod())
+	Draw.BoundedSeries(r, canvasBox, xrange, yrange, s, bbs, bbs.GetPeriod())
 }
 
 func (bbs BollingerBandsSeries) getAverage(valueBuffer *RingBuffer) float64 {

bollinger_band_series_test.go

@@ -11,8 +11,8 @@ func TestBollingerBandSeries(t *testing.T) {
 	assert := assert.New(t)
 
 	s1 := mockValueProvider{
-		X: Seq(1.0, 100.0),
+		X: Sequence.Float64(1.0, 100.0),
-		Y: SeqRand(100, 1024),
+		Y: Sequence.Random(100, 1024),
 	}
 
 	bbs := &BollingerBandsSeries{
@@ -36,8 +36,8 @@ func TestBollingerBandLastValue(t *testing.T) {
 	assert := assert.New(t)
 
 	s1 := mockValueProvider{
-		X: Seq(1.0, 100.0),
+		X: Sequence.Float64(1.0, 100.0),
-		Y: Seq(1.0, 100.0),
+		Y: Sequence.Float64(1.0, 100.0),
 	}
 
 	bbs := &BollingerBandsSeries{

box.go

@@ -66,12 +66,12 @@ func (b Box) GetBottom(defaults ...int) int {
 
 // Width returns the width
 func (b Box) Width() int {
-	return AbsInt(b.Right - b.Left)
+	return Math.AbsInt(b.Right - b.Left)
 }
 
 // Height returns the height
 func (b Box) Height() int {
-	return AbsInt(b.Bottom - b.Top)
+	return Math.AbsInt(b.Bottom - b.Top)
 }
 
 // Center returns the center of the box
@@ -122,10 +122,10 @@ func (b Box) Equals(other Box) bool {
 // Grow grows a box based on another box.
 func (b Box) Grow(other Box) Box {
 	return Box{
-		Top:    MinInt(b.Top, other.Top),
+		Top:    Math.MinInt(b.Top, other.Top),
-		Left:   MinInt(b.Left, other.Left),
+		Left:   Math.MinInt(b.Left, other.Left),
-		Right:  MaxInt(b.Right, other.Right),
+		Right:  Math.MaxInt(b.Right, other.Right),
-		Bottom: MaxInt(b.Bottom, other.Bottom),
+		Bottom: Math.MaxInt(b.Bottom, other.Bottom),
 	}
 }
 
@@ -185,25 +185,12 @@ func (b Box) Fit(other Box) Box {
 // more literally like the opposite of grow.
 func (b Box) Constrain(other Box) Box {
 	newBox := b.Clone()
-	if other.Top < b.Top {
-		delta := b.Top - other.Top
-		newBox.Top = other.Top + delta
-	}
 
-	if other.Left < b.Left {
+	newBox.Top = Math.MaxInt(newBox.Top, other.Top)
-		delta := b.Left - other.Left
+	newBox.Left = Math.MaxInt(newBox.Left, other.Left)
-		newBox.Left = other.Left + delta
+	newBox.Right = Math.MinInt(newBox.Right, other.Right)
-	}
+	newBox.Bottom = Math.MinInt(newBox.Bottom, other.Bottom)
 
-	if other.Right > b.Right {
-		delta := other.Right - b.Right
-		newBox.Right = other.Right - delta
-	}
-
-	if other.Bottom > b.Bottom {
-		delta := other.Bottom - b.Bottom
-		newBox.Bottom = other.Bottom - delta
-	}
 	return newBox
 }
 

box_test.go

@@ -86,6 +86,26 @@ func TestBoxFit(t *testing.T) {
 	assert.True(math.Abs(c.Aspect()-fac.Aspect()) < 0.02)
 }
 
+func TestBoxConstrain(t *testing.T) {
+	assert := assert.New(t)
+
+	a := Box{Top: 64, Left: 64, Right: 192, Bottom: 192}
+	b := Box{Top: 16, Left: 16, Right: 256, Bottom: 170}
+	c := Box{Top: 16, Left: 16, Right: 170, Bottom: 256}
+
+	cab := a.Constrain(b)
+	assert.Equal(64, cab.Top)
+	assert.Equal(64, cab.Left)
+	assert.Equal(192, cab.Right)
+	assert.Equal(170, cab.Bottom)
+
+	cac := a.Constrain(c)
+	assert.Equal(64, cac.Top)
+	assert.Equal(64, cac.Left)
+	assert.Equal(170, cac.Right)
+	assert.Equal(192, cac.Bottom)
+}
+
 func TestBoxOuterConstrain(t *testing.T) {
 	assert := assert.New(t)
 

chart.go

@@ -137,7 +137,7 @@ func (c Chart) getRanges() (xrange, yrange, yrangeAlt Range) {
 	var miny, maxy float64 = math.MaxFloat64, 0
 	var minya, maxya float64 = math.MaxFloat64, 0
 
-	hasSecondaryAxis := false
+	seriesMappedToSecondaryAxis := false
 
 	// note: a possible future optimization is to not scan the series values if
 	// all axis are represented by either custom ticks or custom ranges.
@@ -162,7 +162,7 @@ func (c Chart) getRanges() (xrange, yrange, yrangeAlt Range) {
 						minya = math.Min(minya, vy2)
 						maxya = math.Max(maxya, vy1)
 						maxya = math.Max(maxya, vy2)
-						hasSecondaryAxis = true
+						seriesMappedToSecondaryAxis = true
 					}
 				}
 			} else if vp, isValueProvider := s.(ValueProvider); isValueProvider {
@@ -179,27 +179,42 @@ func (c Chart) getRanges() (xrange, yrange, yrangeAlt Range) {
 					} else if seriesAxis == YAxisSecondary {
 						minya = math.Min(minya, vy)
 						maxya = math.Max(maxya, vy)
-						hasSecondaryAxis = true
+						seriesMappedToSecondaryAxis = true
 					}
 				}
 			}
 		}
 	}
 
+	if c.XAxis.Range == nil {
+		xrange = &ContinuousRange{}
+	} else {
+		xrange = c.XAxis.Range
+	}
+
+	if c.YAxis.Range == nil {
+		yrange = &ContinuousRange{}
+	} else {
+		yrange = c.YAxis.Range
+	}
+
+	if c.YAxisSecondary.Range == nil {
+		yrangeAlt = &ContinuousRange{}
+	} else {
+		yrangeAlt = c.YAxisSecondary.Range
+	}
+
 	if len(c.XAxis.Ticks) > 0 {
 		tickMin, tickMax := math.MaxFloat64, 0.0
 		for _, t := range c.XAxis.Ticks {
 			tickMin = math.Min(tickMin, t.Value)
 			tickMax = math.Max(tickMax, t.Value)
 		}
-		xrange.Min = tickMin
+		xrange.SetMin(tickMin)
-		xrange.Max = tickMax
+		xrange.SetMax(tickMax)
-	} else if !c.XAxis.Range.IsZero() {
+	} else if xrange.IsZero() {
-		xrange.Min = c.XAxis.Range.Min
+		xrange.SetMin(minx)
-		xrange.Max = c.XAxis.Range.Max
+		xrange.SetMax(maxx)
-	} else {
-		xrange.Min = minx
-		xrange.Max = maxx
 	}
 
 	if len(c.YAxis.Ticks) > 0 {
@@ -208,15 +223,17 @@ func (c Chart) getRanges() (xrange, yrange, yrangeAlt Range) {
 			tickMin = math.Min(tickMin, t.Value)
 			tickMax = math.Max(tickMax, t.Value)
 		}
-		yrange.Min = tickMin
+		yrange.SetMin(tickMin)
-		yrange.Max = tickMax
+		yrange.SetMax(tickMax)
-	} else if !c.YAxis.Range.IsZero() {
+	} else if yrange.IsZero() {
-		yrange.Min = c.YAxis.Range.Min
+		yrange.SetMin(miny)
-		yrange.Max = c.YAxis.Range.Max
+		yrange.SetMax(maxy)
-	} else {
+
-		yrange.Min = miny
+		delta := yrange.GetDelta()
-		yrange.Max = maxy
+		roundTo := Math.GetRoundToForDelta(delta)
-		yrange.Min, yrange.Max = yrange.GetRoundedRangeBounds()
+		rmin, rmax := Math.RoundDown(yrange.GetMin(), roundTo), Math.RoundUp(yrange.GetMax(), roundTo)
+		yrange.SetMin(rmin)
+		yrange.SetMax(rmax)
 	}
 
 	if len(c.YAxisSecondary.Ticks) > 0 {
@@ -225,30 +242,31 @@ func (c Chart) getRanges() (xrange, yrange, yrangeAlt Range) {
 			tickMin = math.Min(tickMin, t.Value)
 			tickMax = math.Max(tickMax, t.Value)
 		}
-		yrangeAlt.Min = tickMin
+		yrangeAlt.SetMin(tickMin)
-		yrangeAlt.Max = tickMax
+		yrangeAlt.SetMax(tickMax)
-	} else if !c.YAxisSecondary.Range.IsZero() {
+	} else if seriesMappedToSecondaryAxis && yrangeAlt.IsZero() {
-		yrangeAlt.Min = c.YAxisSecondary.Range.Min
+		yrangeAlt.SetMin(minya)
-		yrangeAlt.Max = c.YAxisSecondary.Range.Max
+		yrangeAlt.SetMax(maxya)
-	} else if hasSecondaryAxis {
+
-		yrangeAlt.Min = minya
+		delta := yrangeAlt.GetDelta()
-		yrangeAlt.Max = maxya
+		roundTo := Math.GetRoundToForDelta(delta)
-		yrangeAlt.Min, yrangeAlt.Max = yrangeAlt.GetRoundedRangeBounds()
+		rmin, rmax := Math.RoundDown(yrangeAlt.GetMin(), roundTo), Math.RoundUp(yrangeAlt.GetMax(), roundTo)
+		yrangeAlt.SetMin(rmin)
+		yrangeAlt.SetMax(rmax)
 	}
 
 	return
 }
 
 func (c Chart) checkRanges(xr, yr, yra Range) error {
-
+	if math.IsInf(xr.GetDelta(), 0) || math.IsNaN(xr.GetDelta()) || xr.GetDelta() == 0 {
-	if math.IsInf(xr.Delta(), 0) || math.IsNaN(xr.Delta()) {
 		return errors.New("Invalid (infinite or NaN) x-range delta")
 	}
-	if math.IsInf(yr.Delta(), 0) || math.IsNaN(yr.Delta()) {
+	if math.IsInf(yr.GetDelta(), 0) || math.IsNaN(yr.GetDelta()) || yr.GetDelta() == 0 {
 		return errors.New("Invalid (infinite or NaN) y-range delta")
 	}
 	if c.hasSecondarySeries() {
-		if math.IsInf(yra.Delta(), 0) || math.IsNaN(yra.Delta()) {
+		if math.IsInf(yra.GetDelta(), 0) || math.IsNaN(yra.GetDelta()) || yra.GetDelta() == 0 {
 			return errors.New("Invalid (infinite or NaN) y-secondary-range delta")
 		}
 	}
@@ -320,14 +338,11 @@ func (c Chart) getAxisAdjustedCanvasBox(r Renderer, canvasBox Box, xr, yr, yra R
 	return canvasBox.OuterConstrain(c.Box(), axesOuterBox)
 }
 
-func (c Chart) setRangeDomains(canvasBox Box, xr, yr, yra Range) (xr2, yr2, yra2 Range) {
+func (c Chart) setRangeDomains(canvasBox Box, xr, yr, yra Range) (Range, Range, Range) {
-	xr2.Min, xr2.Max = xr.Min, xr.Max
+	xr.SetDomain(canvasBox.Width())
-	xr2.Domain = canvasBox.Width()
+	yr.SetDomain(canvasBox.Height())
-	yr2.Min, yr2.Max = yr.Min, yr.Max
+	yra.SetDomain(canvasBox.Height())
-	yr2.Domain = canvasBox.Height()
+	return xr, yr, yra
-	yra2.Min, yra2.Max = yra.Min, yra.Max
-	yra2.Domain = canvasBox.Height()
-	return
 }
 
 func (c Chart) hasAnnotationSeries() bool {
@@ -372,22 +387,22 @@ func (c Chart) getAnnotationAdjustedCanvasBox(r Renderer, canvasBox Box, xr, yr,
 }
 
 func (c Chart) getBackgroundStyle() Style {
-	return c.Background.WithDefaultsFrom(c.styleDefaultsBackground())
+	return c.Background.InheritFrom(c.styleDefaultsBackground())
 }
 
 func (c Chart) drawBackground(r Renderer) {
-	DrawBox(r, Box{
+	Draw.Box(r, Box{
 		Right:  c.GetWidth(),
 		Bottom: c.GetHeight(),
 	}, c.getBackgroundStyle())
 }
 
 func (c Chart) getCanvasStyle() Style {
-	return c.Canvas.WithDefaultsFrom(c.styleDefaultsCanvas())
+	return c.Canvas.InheritFrom(c.styleDefaultsCanvas())
 }
 
 func (c Chart) drawCanvas(r Renderer, canvasBox Box) {
-	DrawBox(r, canvasBox, c.getCanvasStyle())
+	Draw.Box(r, canvasBox, c.getCanvasStyle())
 }
 
 func (c Chart) drawAxes(r Renderer, canvasBox Box, xrange, yrange, yrangeAlt Range, xticks, yticks, yticksAlt []Tick) {
@@ -448,7 +463,7 @@ func (c Chart) styleDefaultsCanvas() Style {
 }
 
 func (c Chart) styleDefaultsSeries(seriesIndex int) Style {
-	strokeColor := GetDefaultSeriesStrokeColor(seriesIndex)
+	strokeColor := GetDefaultColor(seriesIndex)
 	return Style{
 		StrokeColor: strokeColor,
 		StrokeWidth: DefaultStrokeWidth,
@@ -460,6 +475,7 @@ func (c Chart) styleDefaultsSeries(seriesIndex int) Style {
 func (c Chart) styleDefaultsAxis() Style {
 	return Style{
 		Font:        c.GetFont(),
+		FontColor:   DefaultAxisColor,
 		FontSize:    DefaultAxisFontSize,
 		StrokeColor: DefaultAxisColor,
 		StrokeWidth: DefaultAxisLineWidth,

chart_test.go

@@ -77,24 +77,24 @@ func TestChartGetRanges(t *testing.T) {
 	}
 
 	xrange, yrange, yrangeAlt := c.getRanges()
-	assert.Equal(-2.0, xrange.Min)
+	assert.Equal(-2.0, xrange.GetMin())
-	assert.Equal(5.0, xrange.Max)
+	assert.Equal(5.0, xrange.GetMax())
 
-	assert.Equal(-2.1, yrange.Min)
+	assert.Equal(-2.1, yrange.GetMin())
-	assert.Equal(4.5, yrange.Max)
+	assert.Equal(4.5, yrange.GetMax())
 
-	assert.Equal(10.0, yrangeAlt.Min)
+	assert.Equal(10.0, yrangeAlt.GetMin())
-	assert.Equal(14.0, yrangeAlt.Max)
+	assert.Equal(14.0, yrangeAlt.GetMax())
 
 	cSet := Chart{
 		XAxis: XAxis{
-			Range: Range{Min: 9.8, Max: 19.8},
+			Range: &ContinuousRange{Min: 9.8, Max: 19.8},
 		},
 		YAxis: YAxis{
-			Range: Range{Min: 9.9, Max: 19.9},
+			Range: &ContinuousRange{Min: 9.9, Max: 19.9},
 		},
 		YAxisSecondary: YAxis{
-			Range: Range{Min: 9.7, Max: 19.7},
+			Range: &ContinuousRange{Min: 9.7, Max: 19.7},
 		},
 		Series: []Series{
 			ContinuousSeries{
@@ -114,14 +114,14 @@ func TestChartGetRanges(t *testing.T) {
 	}
 
 	xr2, yr2, yra2 := cSet.getRanges()
-	assert.Equal(9.8, xr2.Min)
+	assert.Equal(9.8, xr2.GetMin())
-	assert.Equal(19.8, xr2.Max)
+	assert.Equal(19.8, xr2.GetMax())
 
-	assert.Equal(9.9, yr2.Min)
+	assert.Equal(9.9, yr2.GetMin())
-	assert.Equal(19.9, yr2.Max)
+	assert.Equal(19.9, yr2.GetMax())
 
-	assert.Equal(9.7, yra2.Min)
+	assert.Equal(9.7, yra2.GetMin())
-	assert.Equal(19.7, yra2.Max)
+	assert.Equal(19.7, yra2.GetMax())
 }
 
 func TestChartGetRangesUseTicks(t *testing.T) {
@@ -139,7 +139,7 @@ func TestChartGetRangesUseTicks(t *testing.T) {
 				{4.0, "4.0"},
 				{5.0, "Five"},
 			},
-			Range: Range{
+			Range: &ContinuousRange{
 				Min: -5.0,
 				Max: 5.0,
 			},
@@ -153,10 +153,10 @@ func TestChartGetRangesUseTicks(t *testing.T) {
 	}
 
 	xr, yr, yar := c.getRanges()
-	assert.Equal(-2.0, xr.Min)
+	assert.Equal(-2.0, xr.GetMin())
-	assert.Equal(2.0, xr.Max)
+	assert.Equal(2.0, xr.GetMax())
-	assert.Equal(0.0, yr.Min)
+	assert.Equal(0.0, yr.GetMin())
-	assert.Equal(5.0, yr.Max)
+	assert.Equal(5.0, yr.GetMax())
 	assert.True(yar.IsZero(), yar.String())
 }
 
@@ -165,7 +165,7 @@ func TestChartGetRangesUseUserRanges(t *testing.T) {
 
 	c := Chart{
 		YAxis: YAxis{
-			Range: Range{
+			Range: &ContinuousRange{
 				Min: -5.0,
 				Max: 5.0,
 			},
@@ -179,10 +179,10 @@ func TestChartGetRangesUseUserRanges(t *testing.T) {
 	}
 
 	xr, yr, yar := c.getRanges()
-	assert.Equal(-2.0, xr.Min)
+	assert.Equal(-2.0, xr.GetMin())
-	assert.Equal(2.0, xr.Max)
+	assert.Equal(2.0, xr.GetMax())
-	assert.Equal(-5.0, yr.Min)
+	assert.Equal(-5.0, yr.GetMin())
-	assert.Equal(5.0, yr.Max)
+	assert.Equal(5.0, yr.GetMax())
 	assert.True(yar.IsZero(), yar.String())
 }
 
@@ -310,15 +310,15 @@ func TestChartGetAxesTicks(t *testing.T) {
 	c := Chart{
 		XAxis: XAxis{
 			Style: Style{Show: true},
-			Range: Range{Min: 9.8, Max: 19.8},
+			Range: &ContinuousRange{Min: 9.8, Max: 19.8},
 		},
 		YAxis: YAxis{
 			Style: Style{Show: true},
-			Range: Range{Min: 9.9, Max: 19.9},
+			Range: &ContinuousRange{Min: 9.9, Max: 19.9},
 		},
 		YAxisSecondary: YAxis{
 			Style: Style{Show: true},
-			Range: Range{Min: 9.7, Max: 19.7},
+			Range: &ContinuousRange{Min: 9.7, Max: 19.7},
 		},
 	}
 	xr, yr, yar := c.getRanges()
@@ -337,7 +337,7 @@ func TestChartSingleSeries(t *testing.T) {
 		Width:  1024,
 		Height: 400,
 		YAxis: YAxis{
-			Range: Range{
+			Range: &ContinuousRange{
 				Min: 0.0,
 				Max: 4.0,
 			},
@@ -377,15 +377,15 @@ func TestChartRegressionBadRangesByUser(t *testing.T) {
 
 	c := Chart{
 		YAxis: YAxis{
-			Range: Range{
+			Range: &ContinuousRange{
 				Min: math.Inf(-1),
 				Max: math.Inf(1), // this could really happen? eh.
 			},
 		},
 		Series: []Series{
 			ContinuousSeries{
-				XValues: Seq(1.0, 10.0),
+				XValues: Sequence.Float64(1.0, 10.0),
-				YValues: Seq(1.0, 10.0),
+				YValues: Sequence.Float64(1.0, 10.0),
 			},
 		},
 	}

concat_series.go

@@ -0,0 +1,32 @@
+package chart
+
+// ConcatSeries is a special type of series that concatenates its `InnerSeries`.
+type ConcatSeries []Series
+
+// Len returns the length of the concatenated set of series.
+func (cs ConcatSeries) Len() int {
+	total := 0
+	for _, s := range cs {
+		if typed, isValueProvider := s.(ValueProvider); isValueProvider {
+			total += typed.Len()
+		}
+	}
+
+	return total
+}
+
+// GetValue returns the value at the (meta) index (i.e 0 => totalLen-1)
+func (cs ConcatSeries) GetValue(index int) (x, y float64) {
+	cursor := 0
+	for _, s := range cs {
+		if typed, isValueProvider := s.(ValueProvider); isValueProvider {
+			len := typed.Len()
+			if index < cursor+len {
+				x, y = typed.GetValue(index - cursor) //FENCEPOSTS.
+				return
+			}
+			cursor += typed.Len()
+		}
+	}
+	return
+}

concat_series_test.go

@@ -0,0 +1,41 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestConcatSeries(t *testing.T) {
+	assert := assert.New(t)
+
+	s1 := ContinuousSeries{
+		XValues: Sequence.Float64(1.0, 10.0),
+		YValues: Sequence.Float64(1.0, 10.0),
+	}
+
+	s2 := ContinuousSeries{
+		XValues: Sequence.Float64(11, 20.0),
+		YValues: Sequence.Float64(10.0, 1.0),
+	}
+
+	s3 := ContinuousSeries{
+		XValues: Sequence.Float64(21, 30.0),
+		YValues: Sequence.Float64(1.0, 10.0),
+	}
+
+	cs := ConcatSeries([]Series{s1, s2, s3})
+	assert.Equal(30, cs.Len())
+
+	x0, y0 := cs.GetValue(0)
+	assert.Equal(1.0, x0)
+	assert.Equal(1.0, y0)
+
+	xm, ym := cs.GetValue(19)
+	assert.Equal(20.0, xm)
+	assert.Equal(1.0, ym)
+
+	xn, yn := cs.GetValue(29)
+	assert.Equal(30.0, xn)
+	assert.Equal(10.0, yn)
+}

continuous_range.go

@@ -0,0 +1,67 @@
+package chart
+
+import (
+	"fmt"
+	"math"
+)
+
+// ContinuousRange represents a boundary for a set of numbers.
+type ContinuousRange struct {
+	Min    float64
+	Max    float64
+	Domain int
+}
+
+// IsZero returns if the ContinuousRange has been set or not.
+func (r ContinuousRange) IsZero() bool {
+	return (r.Min == 0 || math.IsNaN(r.Min)) &&
+		(r.Max == 0 || math.IsNaN(r.Max)) &&
+		r.Domain == 0
+}
+
+// GetMin gets the min value for the continuous range.
+func (r ContinuousRange) GetMin() float64 {
+	return r.Min
+}
+
+// SetMin sets the min value for the continuous range.
+func (r *ContinuousRange) SetMin(min float64) {
+	r.Min = min
+}
+
+// GetMax returns the max value for the continuous range.
+func (r ContinuousRange) GetMax() float64 {
+	return r.Max
+}
+
+// SetMax sets the max value for the continuous range.
+func (r *ContinuousRange) SetMax(max float64) {
+	r.Max = max
+}
+
+// GetDelta returns the difference between the min and max value.
+func (r ContinuousRange) GetDelta() float64 {
+	return r.Max - r.Min
+}
+
+// GetDomain returns the range domain.
+func (r ContinuousRange) GetDomain() int {
+	return r.Domain
+}
+
+// SetDomain sets the range domain.
+func (r *ContinuousRange) SetDomain(domain int) {
+	r.Domain = domain
+}
+
+// String returns a simple string for the ContinuousRange.
+func (r ContinuousRange) String() string {
+	return fmt.Sprintf("ContinuousRange [%.2f,%.2f] => %d", r.Min, r.Max, r.Domain)
+}
+
+// Translate maps a given value into the ContinuousRange space.
+func (r ContinuousRange) Translate(value float64) int {
+	normalized := value - r.Min
+	ratio := normalized / r.GetDelta()
+	return int(math.Ceil(ratio * float64(r.Domain)))
+}

continuous_range_test.go

@@ -9,8 +9,8 @@ import (
 func TestRangeTranslate(t *testing.T) {
 	assert := assert.New(t)
 	values := []float64{1.0, 2.0, 2.5, 2.7, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0}
-	r := Range{Domain: 1000}
+	r := ContinuousRange{Domain: 1000}
-	r.Min, r.Max = MinAndMax(values...)
+	r.Min, r.Max = Math.MinAndMax(values...)
 
 	// delta = ~7.0
 	// value = ~5.0

continuous_series.go

@@ -5,7 +5,7 @@ type ContinuousSeries struct {
 	Name  string
 	Style Style
 
-	YAxis YAxisType
+	YAxis yAxisType
 
 	XValues []float64
 	YValues []float64
@@ -44,12 +44,12 @@ func (cs ContinuousSeries) GetValueFormatters() (x, y ValueFormatter) {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (cs ContinuousSeries) GetYAxis() YAxisType {
+func (cs ContinuousSeries) GetYAxis() yAxisType {
 	return cs.YAxis
 }
 
 // Render renders the series.
 func (cs ContinuousSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	style := cs.Style.WithDefaultsFrom(defaults)
+	style := cs.Style.InheritFrom(defaults)
-	DrawLineSeries(r, canvasBox, xrange, yrange, style, cs)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, cs)
 }

continuous_series_test.go

@@ -0,0 +1,31 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestContinuousSeries(t *testing.T) {
+	assert := assert.New(t)
+
+	cs := ContinuousSeries{
+		Name:    "Test Series",
+		XValues: Sequence.Float64(1.0, 10.0),
+		YValues: Sequence.Float64(1.0, 10.0),
+	}
+
+	assert.Equal("Test Series", cs.GetName())
+	assert.Equal(10, cs.Len())
+	x0, y0 := cs.GetValue(0)
+	assert.Equal(1.0, x0)
+	assert.Equal(1.0, y0)
+
+	xn, yn := cs.GetValue(9)
+	assert.Equal(10.0, xn)
+	assert.Equal(10.0, yn)
+
+	xn, yn = cs.GetLastValue()
+	assert.Equal(10.0, xn)
+	assert.Equal(10.0, yn)
+}

date/util.go

@@ -0,0 +1,353 @@
+package date
+
+import (
+	"sync"
+	"time"
+)
+
+const (
+	// AllDaysMask is a bitmask of all the days of the week.
+	AllDaysMask = 1<<uint(time.Sunday) | 1<<uint(time.Monday) | 1<<uint(time.Tuesday) | 1<<uint(time.Wednesday) | 1<<uint(time.Thursday) | 1<<uint(time.Friday) | 1<<uint(time.Saturday)
+	// WeekDaysMask is a bitmask of all the weekdays of the week.
+	WeekDaysMask = 1<<uint(time.Monday) | 1<<uint(time.Tuesday) | 1<<uint(time.Wednesday) | 1<<uint(time.Thursday) | 1<<uint(time.Friday)
+	//WeekendDaysMask is a bitmask of the weekend days of the week.
+	WeekendDaysMask = 1<<uint(time.Sunday) | 1<<uint(time.Saturday)
+)
+
+var (
+	// DaysOfWeek are all the time.Weekday in an array for utility purposes.
+	DaysOfWeek = []time.Weekday{
+		time.Sunday,
+		time.Monday,
+		time.Tuesday,
+		time.Wednesday,
+		time.Thursday,
+		time.Friday,
+		time.Saturday,
+	}
+
+	// WeekDays are the business time.Weekday in an array.
+	WeekDays = []time.Weekday{
+		time.Monday,
+		time.Tuesday,
+		time.Wednesday,
+		time.Thursday,
+		time.Friday,
+	}
+
+	// WeekendDays are the weekend time.Weekday in an array.
+	WeekendDays = []time.Weekday{
+		time.Sunday,
+		time.Saturday,
+	}
+
+	//Epoch is unix epoc saved for utility purposes.
+	Epoch = time.Unix(0, 0)
+)
+
+var (
+	_easternLock sync.Mutex
+	_eastern     *time.Location
+)
+
+var (
+	// NYSEOpen is when the NYSE opens.
+	NYSEOpen = ClockTime(9, 30, 0, 0, Eastern())
+
+	// NYSEClose is when the NYSE closes.
+	NYSEClose = ClockTime(16, 0, 0, 0, Eastern())
+
+	// NASDAQOpen is when NASDAQ opens.
+	NASDAQOpen = ClockTime(9, 30, 0, 0, Eastern())
+
+	// NASDAQClose is when NASDAQ closes.
+	NASDAQClose = ClockTime(16, 0, 0, 0, Eastern())
+
+	// NYSEArcaOpen is when NYSEARCA opens.
+	NYSEArcaOpen = ClockTime(4, 0, 0, 0, Eastern())
+
+	// NYSEArcaClose is when NYSEARCA closes.
+	NYSEArcaClose = ClockTime(20, 0, 0, 0, Eastern())
+)
+
+// HolidayProvider is a function that returns if a given time falls on a holiday.
+type HolidayProvider func(time.Time) bool
+
+// DefaultHolidayProvider implements `HolidayProvider` and just returns false.
+func DefaultHolidayProvider(_ time.Time) bool { return false }
+
+// IsNYSEHoliday returns if a date was/is on a nyse holiday day.
+func IsNYSEHoliday(t time.Time) bool {
+	te := t.In(Eastern())
+	if te.Year() == 2013 {
+		if te.Month() == 1 {
+			return te.Day() == 1 || te.Day() == 21
+		} else if te.Month() == 2 {
+			return te.Day() == 18
+		} else if te.Month() == 3 {
+			return te.Day() == 29
+		} else if te.Month() == 5 {
+			return te.Day() == 27
+		} else if te.Month() == 7 {
+			return te.Day() == 4
+		} else if te.Month() == 9 {
+			return te.Day() == 2
+		} else if te.Month() == 11 {
+			return te.Day() == 28
+		} else if te.Month() == 12 {
+			return te.Day() == 25
+		}
+	} else if te.Year() == 2014 {
+		if te.Month() == 1 {
+			return te.Day() == 1 || te.Day() == 20
+		} else if te.Month() == 2 {
+			return te.Day() == 17
+		} else if te.Month() == 4 {
+			return te.Day() == 18
+		} else if te.Month() == 5 {
+			return te.Day() == 26
+		} else if te.Month() == 7 {
+			return te.Day() == 4
+		} else if te.Month() == 9 {
+			return te.Day() == 1
+		} else if te.Month() == 11 {
+			return te.Day() == 27
+		} else if te.Month() == 12 {
+			return te.Day() == 25
+		}
+	} else if te.Year() == 2015 {
+		if te.Month() == 1 {
+			return te.Day() == 1 || te.Day() == 19
+		} else if te.Month() == 2 {
+			return te.Day() == 16
+		} else if te.Month() == 4 {
+			return te.Day() == 3
+		} else if te.Month() == 5 {
+			return te.Day() == 25
+		} else if te.Month() == 7 {
+			return te.Day() == 3
+		} else if te.Month() == 9 {
+			return te.Day() == 7
+		} else if te.Month() == 11 {
+			return te.Day() == 26
+		} else if te.Month() == 12 {
+			return te.Day() == 25
+		}
+	} else if te.Year() == 2016 {
+		if te.Month() == 1 {
+			return te.Day() == 1 || te.Day() == 18
+		} else if te.Month() == 2 {
+			return te.Day() == 15
+		} else if te.Month() == 3 {
+			return te.Day() == 25
+		} else if te.Month() == 5 {
+			return te.Day() == 30
+		} else if te.Month() == 7 {
+			return te.Day() == 4
+		} else if te.Month() == 9 {
+			return te.Day() == 5
+		} else if te.Month() == 11 {
+			return te.Day() == 24 || te.Day() == 25
+		} else if te.Month() == 12 {
+			return te.Day() == 26
+		}
+	} else if te.Year() == 2017 {
+		if te.Month() == 1 {
+			return te.Day() == 1 || te.Day() == 16
+		} else if te.Month() == 2 {
+			return te.Day() == 20
+		} else if te.Month() == 4 {
+			return te.Day() == 15
+		} else if te.Month() == 5 {
+			return te.Day() == 29
+		} else if te.Month() == 7 {
+			return te.Day() == 4
+		} else if te.Month() == 9 {
+			return te.Day() == 4
+		} else if te.Month() == 11 {
+			return te.Day() == 23
+		} else if te.Month() == 12 {
+			return te.Day() == 25
+		}
+	} else if te.Year() == 2018 {
+		if te.Month() == 1 {
+			return te.Day() == 1 || te.Day() == 15
+		} else if te.Month() == 2 {
+			return te.Day() == 19
+		} else if te.Month() == 3 {
+			return te.Day() == 30
+		} else if te.Month() == 5 {
+			return te.Day() == 28
+		} else if te.Month() == 7 {
+			return te.Day() == 4
+		} else if te.Month() == 9 {
+			return te.Day() == 3
+		} else if te.Month() == 11 {
+			return te.Day() == 22
+		} else if te.Month() == 12 {
+			return te.Day() == 25
+		}
+	}
+	return false
+}
+
+// IsNYSEArcaHoliday returns that returns if a given time falls on a holiday.
+func IsNYSEArcaHoliday(t time.Time) bool {
+	return IsNYSEHoliday(t)
+}
+
+// IsNASDAQHoliday returns if a date was a NASDAQ holiday day.
+func IsNASDAQHoliday(t time.Time) bool {
+	return IsNYSEHoliday(t)
+}
+
+// Eastern returns the eastern timezone.
+func Eastern() *time.Location {
+	if _eastern == nil {
+		_easternLock.Lock()
+		defer _easternLock.Unlock()
+		if _eastern == nil {
+			_eastern, _ = time.LoadLocation("America/New_York")
+		}
+	}
+	return _eastern
+}
+
+// ClockTime returns a new time.Time for the given clock components.
+func ClockTime(hour, min, sec, nsec int, loc *time.Location) time.Time {
+	return time.Date(0, 0, 0, hour, min, sec, nsec, loc)
+}
+
+// On returns the clock components of clock (hour,minute,second) on the date components of d.
+func On(clock, d time.Time) time.Time {
+	return time.Date(d.Year(), d.Month(), d.Day(), clock.Hour(), clock.Minute(), clock.Second(), clock.Nanosecond(), clock.Location())
+}
+
+// Optional returns a pointer reference to a given time.
+func Optional(t time.Time) *time.Time {
+	return &t
+}
+
+// IsWeekDay returns if the day is a monday->friday.
+func IsWeekDay(day time.Weekday) bool {
+	return !IsWeekendDay(day)
+}
+
+// IsWeekendDay returns if the day is a monday->friday.
+func IsWeekendDay(day time.Weekday) bool {
+	return day == time.Saturday || day == time.Sunday
+}
+
+// BeforeDate returns if a timestamp is strictly before another date (ignoring hours, minutes etc.)
+func BeforeDate(before, reference time.Time) bool {
+	if before.Year() < reference.Year() {
+		return true
+	}
+	if before.Month() < reference.Month() {
+		return true
+	}
+	return before.Year() == reference.Year() && before.Month() == reference.Month() && before.Day() < reference.Day()
+}
+
+// NextMarketOpen returns the next market open after a given time.
+func NextMarketOpen(after, openTime time.Time, isHoliday HolidayProvider) time.Time {
+	afterEastern := after.In(Eastern())
+	todaysOpen := On(openTime, afterEastern)
+
+	if isHoliday == nil {
+		isHoliday = DefaultHolidayProvider
+	}
+
+	if afterEastern.Before(todaysOpen) && IsWeekDay(todaysOpen.Weekday()) && !isHoliday(todaysOpen) {
+		return todaysOpen
+	}
+
+	if afterEastern.Equal(todaysOpen) { //rare but it might happen.
+		return todaysOpen
+	}
+
+	for cursorDay := 1; cursorDay < 6; cursorDay++ {
+		newDay := todaysOpen.AddDate(0, 0, cursorDay)
+		if IsWeekDay(newDay.Weekday()) && !isHoliday(afterEastern) {
+			return On(openTime, newDay)
+		}
+	}
+	return Epoch //we should never reach this.
+}
+
+// NextMarketClose returns the next market close after a given time.
+func NextMarketClose(after, closeTime time.Time, isHoliday HolidayProvider) time.Time {
+	afterEastern := after.In(Eastern())
+
+	if isHoliday == nil {
+		isHoliday = DefaultHolidayProvider
+	}
+
+	todaysClose := On(closeTime, afterEastern)
+	if afterEastern.Before(todaysClose) && IsWeekDay(todaysClose.Weekday()) && !isHoliday(todaysClose) {
+		return todaysClose
+	}
+
+	if afterEastern.Equal(todaysClose) { //rare but it might happen.
+		return todaysClose
+	}
+
+	for cursorDay := 1; cursorDay < 6; cursorDay++ {
+		newDay := todaysClose.AddDate(0, 0, cursorDay)
+		if IsWeekDay(newDay.Weekday()) && !isHoliday(newDay) {
+			return On(closeTime, newDay)
+		}
+	}
+	return Epoch //we should never reach this.
+}
+
+// CalculateMarketSecondsBetween calculates the number of seconds the market was open between two dates.
+func CalculateMarketSecondsBetween(start, end, marketOpen, marketClose time.Time, isHoliday HolidayProvider) (seconds int64) {
+	startEastern := start.In(Eastern())
+	endEastern := end.In(Eastern())
+
+	startMarketOpen := On(marketOpen, startEastern)
+	startMarketClose := On(marketClose, startEastern)
+
+	if !IsWeekendDay(startMarketOpen.Weekday()) && !isHoliday(startMarketOpen) {
+		if (startEastern.Equal(startMarketOpen) || startEastern.After(startMarketOpen)) && startEastern.Before(startMarketClose) {
+			if endEastern.Before(startMarketClose) {
+				seconds += int64(endEastern.Sub(startEastern) / time.Second)
+			} else {
+				seconds += int64(startMarketClose.Sub(startEastern) / time.Second)
+			}
+		}
+	}
+
+	cursor := NextMarketOpen(startMarketClose, marketOpen, isHoliday)
+	for BeforeDate(cursor, endEastern) {
+		if IsWeekDay(cursor.Weekday()) && !isHoliday(cursor) {
+			close := NextMarketClose(cursor, marketClose, isHoliday)
+			seconds += int64(close.Sub(cursor) / time.Second)
+		}
+		cursor = cursor.AddDate(0, 0, 1)
+	}
+
+	finalMarketOpen := NextMarketOpen(cursor, marketOpen, isHoliday)
+	finalMarketClose := NextMarketClose(cursor, marketClose, isHoliday)
+	if endEastern.After(finalMarketOpen) {
+		if endEastern.Before(finalMarketClose) {
+			seconds += int64(endEastern.Sub(finalMarketOpen) / time.Second)
+		} else {
+			seconds += int64(finalMarketClose.Sub(finalMarketOpen) / time.Second)
+		}
+	}
+
+	return
+}
+
+// Format returns a string representation of a date.
+func format(t time.Time) string {
+	return t.Format("2006-01-02")
+}
+
+// Parse parses a date from a string.
+func parse(str string) time.Time {
+	res, _ := time.Parse("2006-01-02", str)
+	return res
+}

date/util_test.go

@@ -0,0 +1,98 @@
+package date
+
+import (
+	"testing"
+	"time"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestBeforeDate(t *testing.T) {
+	assert := assert.New(t)
+
+	assert.True(BeforeDate(parse("2015-07-02"), parse("2016-07-01")))
+	assert.True(BeforeDate(parse("2016-06-01"), parse("2016-07-01")))
+	assert.True(BeforeDate(parse("2016-07-01"), parse("2016-07-02")))
+
+	assert.False(BeforeDate(parse("2016-07-01"), parse("2016-07-01")))
+	assert.False(BeforeDate(parse("2016-07-03"), parse("2016-07-01")))
+	assert.False(BeforeDate(parse("2016-08-03"), parse("2016-07-01")))
+	assert.False(BeforeDate(parse("2017-08-03"), parse("2016-07-01")))
+}
+
+func TestNextMarketOpen(t *testing.T) {
+	assert := assert.New(t)
+
+	beforeOpen := time.Date(2016, 07, 18, 9, 0, 0, 0, Eastern())
+	todayOpen := time.Date(2016, 07, 18, 9, 30, 0, 0, Eastern())
+
+	afterOpen := time.Date(2016, 07, 18, 9, 31, 0, 0, Eastern())
+	tomorrowOpen := time.Date(2016, 07, 19, 9, 30, 0, 0, Eastern())
+
+	afterFriday := time.Date(2016, 07, 22, 9, 31, 0, 0, Eastern())
+	mondayOpen := time.Date(2016, 07, 25, 9, 30, 0, 0, Eastern())
+
+	weekend := time.Date(2016, 07, 23, 9, 31, 0, 0, Eastern())
+
+	assert.True(todayOpen.Equal(NextMarketOpen(beforeOpen, NYSEOpen, IsNYSEHoliday)))
+	assert.True(tomorrowOpen.Equal(NextMarketOpen(afterOpen, NYSEOpen, IsNYSEHoliday)))
+	assert.True(mondayOpen.Equal(NextMarketOpen(afterFriday, NYSEOpen, IsNYSEHoliday)))
+	assert.True(mondayOpen.Equal(NextMarketOpen(weekend, NYSEOpen, IsNYSEHoliday)))
+
+	testRegression := time.Date(2016, 07, 18, 16, 0, 0, 0, Eastern())
+	shouldbe := time.Date(2016, 07, 19, 9, 30, 0, 0, Eastern())
+
+	assert.True(shouldbe.Equal(NextMarketOpen(testRegression, NYSEOpen, IsNYSEHoliday)))
+}
+
+func TestNextMarketClose(t *testing.T) {
+	assert := assert.New(t)
+
+	beforeClose := time.Date(2016, 07, 18, 15, 0, 0, 0, Eastern())
+	todayClose := time.Date(2016, 07, 18, 16, 00, 0, 0, Eastern())
+
+	afterClose := time.Date(2016, 07, 18, 16, 1, 0, 0, Eastern())
+	tomorrowClose := time.Date(2016, 07, 19, 16, 00, 0, 0, Eastern())
+
+	afterFriday := time.Date(2016, 07, 22, 16, 1, 0, 0, Eastern())
+	mondayClose := time.Date(2016, 07, 25, 16, 0, 0, 0, Eastern())
+
+	weekend := time.Date(2016, 07, 23, 9, 31, 0, 0, Eastern())
+
+	assert.True(todayClose.Equal(NextMarketClose(beforeClose, NYSEClose, IsNYSEHoliday)))
+	assert.True(tomorrowClose.Equal(NextMarketClose(afterClose, NYSEClose, IsNYSEHoliday)))
+	assert.True(mondayClose.Equal(NextMarketClose(afterFriday, NYSEClose, IsNYSEHoliday)))
+	assert.True(mondayClose.Equal(NextMarketClose(weekend, NYSEClose, IsNYSEHoliday)))
+}
+
+func TestCalculateMarketSecondsBetween(t *testing.T) {
+	assert := assert.New(t)
+
+	start := time.Date(2016, 07, 18, 9, 30, 0, 0, Eastern())
+	end := time.Date(2016, 07, 22, 16, 00, 0, 0, Eastern())
+
+	shouldbe := 5 * 6.5 * 60 * 60
+
+	assert.Equal(shouldbe, CalculateMarketSecondsBetween(start, end, NYSEOpen, NYSEClose, IsNYSEHoliday))
+}
+
+func TestCalculateMarketSecondsBetween1D(t *testing.T) {
+	assert := assert.New(t)
+
+	start := time.Date(2016, 07, 22, 9, 45, 0, 0, Eastern())
+	end := time.Date(2016, 07, 22, 15, 45, 0, 0, Eastern())
+
+	shouldbe := 6 * 60 * 60
+
+	assert.Equal(shouldbe, CalculateMarketSecondsBetween(start, end, NYSEOpen, NYSEClose, IsNYSEHoliday))
+}
+
+func TestCalculateMarketSecondsBetweenLTM(t *testing.T) {
+	assert := assert.New(t)
+
+	start := time.Date(2015, 07, 01, 9, 30, 0, 0, Eastern())
+	end := time.Date(2016, 07, 01, 9, 30, 0, 0, Eastern())
+
+	shouldbe := 253 * 6.5 * 60 * 60 //253 full market days since this date last year.
+	assert.Equal(shouldbe, CalculateMarketSecondsBetween(start, end, NYSEOpen, NYSEClose, IsNYSEHoliday))
+}

defaults.go

@@ -2,7 +2,6 @@ package chart
 
 import (
 	"sync"
-	"time"
 
 	"github.com/golang/freetype/truetype"
 	"github.com/wcharczuk/go-chart/drawing"
@@ -34,6 +33,9 @@ const (
 	// DefaultTitleTop is the default distance from the top of the chart to put the title.
 	DefaultTitleTop = 10
 
+	// DefaultLineSpacing is the default vertical distance between lines of text.
+	DefaultLineSpacing = 5
+
 	// DefaultYAxisMargin is the default distance from the right of the canvas to the y axis labels.
 	DefaultYAxisMargin = 10
 	// DefaultXAxisMargin is the default distance from bottom of the canvas to the x axis labels.
@@ -59,7 +61,7 @@ const (
 	// DefaultDateHourFormat is the date format for hour timestamp formats.
 	DefaultDateHourFormat = "01-02 3PM"
 	// DefaultDateMinuteFormat is the date format for minute range timestamp formats.
-	DefaultDateMinuteFormat = time.Kitchen
+	DefaultDateMinuteFormat = "01-02 3:04PM"
 	// DefaultFloatFormat is the default float format.
 	DefaultFloatFormat = "%.2f"
 	// DefaultPercentValueFormat is the default percent format.
@@ -67,42 +69,89 @@ const (
 )
 
 var (
-	// DefaultBackgroundColor is the default chart background color.
+	// ColorWhite is white.
-	// It is equivalent to css color:white.
+	ColorWhite = drawing.Color{R: 255, G: 255, B: 255, A: 255}
-	DefaultBackgroundColor = drawing.Color{R: 255, G: 255, B: 255, A: 255}
+	// ColorBlue is the basic theme blue color.
-	// DefaultBackgroundStrokeColor is the default chart border color.
+	ColorBlue = drawing.Color{R: 0, G: 116, B: 217, A: 255}
-	// It is equivalent to color:white.
+	// ColorCyan is the basic theme cyan color.
-	DefaultBackgroundStrokeColor = drawing.Color{R: 255, G: 255, B: 255, A: 255}
+	ColorCyan = drawing.Color{R: 0, G: 217, B: 210, A: 255}
-	// DefaultCanvasColor is the default chart canvas color.
+	// ColorGreen is the basic theme green color.
-	// It is equivalent to css color:white.
+	ColorGreen = drawing.Color{R: 0, G: 217, B: 101, A: 255}
-	DefaultCanvasColor = drawing.Color{R: 255, G: 255, B: 255, A: 255}
+	// ColorRed is the basic theme red color.
-	// DefaultCanvasStrokeColor is the default chart canvas stroke color.
+	ColorRed = drawing.Color{R: 217, G: 0, B: 116, A: 255}
-	// It is equivalent to css color:white.
+	// ColorOrange is the basic theme orange color.
-	DefaultCanvasStrokeColor = drawing.Color{R: 255, G: 255, B: 255, A: 255}
+	ColorOrange = drawing.Color{R: 217, G: 101, B: 0, A: 255}
-	// DefaultTextColor is the default chart text color.
+	// ColorYellow is the basic theme yellow color.
-	// It is equivalent to #333333.
+	ColorYellow = drawing.Color{R: 217, G: 210, B: 0, A: 255}
-	DefaultTextColor = drawing.Color{R: 51, G: 51, B: 51, A: 255}
+	// ColorBlack is the basic theme black color.
-	// DefaultAxisColor is the default chart axis line color.
+	ColorBlack = drawing.Color{R: 51, G: 51, B: 51, A: 255}
-	// It is equivalent to #333333.
+	// ColorLightGray is the basic theme light gray color.
-	DefaultAxisColor = drawing.Color{R: 51, G: 51, B: 51, A: 255}
+	ColorLightGray = drawing.Color{R: 239, G: 239, B: 239, A: 255}
-	// DefaultStrokeColor is the default chart border color.
+
-	// It is equivalent to #efefef.
+	// ColorAlternateBlue is a alternate theme color.
-	DefaultStrokeColor = drawing.Color{R: 239, G: 239, B: 239, A: 255}
+	ColorAlternateBlue = drawing.Color{R: 106, G: 195, B: 203, A: 255}
-	// DefaultFillColor is the default fill color.
+	// ColorAlternateGreen is a alternate theme color.
-	// It is equivalent to #0074d9.
+	ColorAlternateGreen = drawing.Color{R: 42, G: 190, B: 137, A: 255}
-	DefaultFillColor = drawing.Color{R: 0, G: 217, B: 116, A: 255}
+	// ColorAlternateGray is a alternate theme color.
-	// DefaultAnnotationFillColor is the default annotation background color.
+	ColorAlternateGray = drawing.Color{R: 110, G: 128, B: 139, A: 255}
-	DefaultAnnotationFillColor = drawing.Color{R: 255, G: 255, B: 255, A: 255}
+	// ColorAlternateYellow is a alternate theme color.
-	// DefaultGridLineColor is the default grid line color.
+	ColorAlternateYellow = drawing.Color{R: 240, G: 174, B: 90, A: 255}
-	DefaultGridLineColor = drawing.Color{R: 239, G: 239, B: 239, A: 255}
+	// ColorAlternateLightGray is a alternate theme color.
+	ColorAlternateLightGray = drawing.Color{R: 187, G: 190, B: 191, A: 255}
 )
 
 var (
-	// DefaultSeriesStrokeColors are a couple default series colors.
+	// DefaultBackgroundColor is the default chart background color.
-	DefaultSeriesStrokeColors = []drawing.Color{
+	// It is equivalent to css color:white.
-		{R: 0, G: 116, B: 217, A: 255},
+	DefaultBackgroundColor = ColorWhite
-		{R: 0, G: 217, B: 116, A: 255},
+	// DefaultBackgroundStrokeColor is the default chart border color.
-		{R: 217, G: 0, B: 116, A: 255},
+	// It is equivalent to color:white.
+	DefaultBackgroundStrokeColor = ColorWhite
+	// DefaultCanvasColor is the default chart canvas color.
+	// It is equivalent to css color:white.
+	DefaultCanvasColor = ColorWhite
+	// DefaultCanvasStrokeColor is the default chart canvas stroke color.
+	// It is equivalent to css color:white.
+	DefaultCanvasStrokeColor = ColorWhite
+	// DefaultTextColor is the default chart text color.
+	// It is equivalent to #333333.
+	DefaultTextColor = ColorBlack
+	// DefaultAxisColor is the default chart axis line color.
+	// It is equivalent to #333333.
+	DefaultAxisColor = ColorBlack
+	// DefaultStrokeColor is the default chart border color.
+	// It is equivalent to #efefef.
+	DefaultStrokeColor = ColorLightGray
+	// DefaultFillColor is the default fill color.
+	// It is equivalent to #0074d9.
+	DefaultFillColor = ColorBlue
+	// DefaultAnnotationFillColor is the default annotation background color.
+	DefaultAnnotationFillColor = ColorWhite
+	// DefaultGridLineColor is the default grid line color.
+	DefaultGridLineColor = ColorLightGray
+)
+
+var (
+	// DefaultColors are a couple default series colors.
+	DefaultColors = []drawing.Color{
+		ColorBlue,
+		ColorGreen,
+		ColorRed,
+		ColorCyan,
+		ColorOrange,
+	}
+
+	// DefaultAlternateColors are a couple alternate colors.
+	DefaultAlternateColors = []drawing.Color{
+		ColorAlternateBlue,
+		ColorAlternateGreen,
+		ColorAlternateGray,
+		ColorAlternateYellow,
+		ColorBlue,
+		ColorGreen,
+		ColorRed,
+		ColorCyan,
+		ColorOrange,
 	}
 )
 
@@ -117,11 +166,18 @@ var (
 	DashArrayDashesLarge = []int{10, 10}
 )
 
-// GetDefaultSeriesStrokeColor returns a color from the default list by index.
+// GetDefaultColor returns a color from the default list by index.
-// NOTE: the index will wrap around (using a modulo).g
+// NOTE: the index will wrap around (using a modulo).
-func GetDefaultSeriesStrokeColor(index int) drawing.Color {
+func GetDefaultColor(index int) drawing.Color {
-	finalIndex := index % len(DefaultSeriesStrokeColors)
+	finalIndex := index % len(DefaultColors)
-	return DefaultSeriesStrokeColors[finalIndex]
+	return DefaultColors[finalIndex]
+}
+
+// GetAlternateColor returns a color from the default list by index.
+// NOTE: the index will wrap around (using a modulo).
+func GetAlternateColor(index int) drawing.Color {
+	finalIndex := index % len(DefaultAlternateColors)
+	return DefaultAlternateColors[finalIndex]
 }
 
 var (

draw.go

@@ -0,0 +1,256 @@
+package chart
+
+import "math"
+
+var (
+	// Draw contains helpers for drawing common objects.
+	Draw = &draw{}
+)
+
+type draw struct{}
+
+// LineSeries draws a line series with a renderer.
+func (d draw) LineSeries(r Renderer, canvasBox Box, xrange, yrange Range, style Style, vs ValueProvider) {
+	if vs.Len() == 0 {
+		return
+	}
+
+	cb := canvasBox.Bottom
+	cl := canvasBox.Left
+
+	v0x, v0y := vs.GetValue(0)
+	x0 := cl + xrange.Translate(v0x)
+	y0 := cb - yrange.Translate(v0y)
+
+	var vx, vy float64
+	var x, y int
+
+	fill := style.GetFillColor()
+	if !fill.IsZero() {
+		r.SetFillColor(fill)
+		r.MoveTo(x0, y0)
+		for i := 1; i < vs.Len(); i++ {
+			vx, vy = vs.GetValue(i)
+			x = cl + xrange.Translate(vx)
+			y = cb - yrange.Translate(vy)
+			r.LineTo(x, y)
+		}
+		r.LineTo(x, cb)
+		r.LineTo(x0, cb)
+		r.Close()
+		r.Fill()
+	}
+
+	style.GetStrokeOptions().WriteToRenderer(r)
+
+	r.MoveTo(x0, y0)
+	for i := 1; i < vs.Len(); i++ {
+		vx, vy = vs.GetValue(i)
+		x = cl + xrange.Translate(vx)
+		y = cb - yrange.Translate(vy)
+		r.LineTo(x, y)
+	}
+	r.Stroke()
+}
+
+// BoundedSeries draws a series that implements BoundedValueProvider.
+func (d draw) BoundedSeries(r Renderer, canvasBox Box, xrange, yrange Range, style Style, bbs BoundedValueProvider, drawOffsetIndexes ...int) {
+	drawOffsetIndex := 0
+	if len(drawOffsetIndexes) > 0 {
+		drawOffsetIndex = drawOffsetIndexes[0]
+	}
+
+	cb := canvasBox.Bottom
+	cl := canvasBox.Left
+
+	v0x, v0y1, v0y2 := bbs.GetBoundedValue(0)
+	x0 := cl + xrange.Translate(v0x)
+	y0 := cb - yrange.Translate(v0y1)
+
+	var vx, vy1, vy2 float64
+	var x, y int
+
+	xvalues := make([]float64, bbs.Len())
+	xvalues[0] = v0x
+	y2values := make([]float64, bbs.Len())
+	y2values[0] = v0y2
+
+	style.GetFillAndStrokeOptions().WriteToRenderer(r)
+	r.MoveTo(x0, y0)
+	for i := 1; i < bbs.Len(); i++ {
+		vx, vy1, vy2 = bbs.GetBoundedValue(i)
+
+		xvalues[i] = vx
+		y2values[i] = vy2
+
+		x = cl + xrange.Translate(vx)
+		y = cb - yrange.Translate(vy1)
+		if i > drawOffsetIndex {
+			r.LineTo(x, y)
+		} else {
+			r.MoveTo(x, y)
+		}
+	}
+	y = cb - yrange.Translate(vy2)
+	r.LineTo(x, y)
+	for i := bbs.Len() - 1; i >= drawOffsetIndex; i-- {
+		vx, vy2 = xvalues[i], y2values[i]
+		x = cl + xrange.Translate(vx)
+		y = cb - yrange.Translate(vy2)
+		r.LineTo(x, y)
+	}
+	r.Close()
+	r.FillStroke()
+}
+
+// HistogramSeries draws a value provider as boxes from 0.
+func (d draw) HistogramSeries(r Renderer, canvasBox Box, xrange, yrange Range, style Style, vs ValueProvider, barWidths ...int) {
+	if vs.Len() == 0 {
+		return
+	}
+
+	//calculate bar width?
+	seriesLength := vs.Len()
+	barWidth := int(math.Floor(float64(xrange.GetDomain()) / float64(seriesLength)))
+	if len(barWidths) > 0 {
+		barWidth = barWidths[0]
+	}
+
+	cb := canvasBox.Bottom
+	cl := canvasBox.Left
+
+	//foreach datapoint, draw a box.
+	for index := 0; index < seriesLength; index++ {
+		vx, vy := vs.GetValue(index)
+		y0 := yrange.Translate(0)
+		x := cl + xrange.Translate(vx)
+		y := yrange.Translate(vy)
+
+		d.Box(r, Box{
+			Top:    cb - y0,
+			Left:   x - (barWidth >> 1),
+			Right:  x + (barWidth >> 1),
+			Bottom: cb - y,
+		}, style)
+	}
+}
+
+// MeasureAnnotation measures how big an annotation would be.
+func (d draw) MeasureAnnotation(r Renderer, canvasBox Box, style Style, lx, ly int, label string) Box {
+	style.WriteToRenderer(r)
+
+	textBox := r.MeasureText(label)
+	textWidth := textBox.Width()
+	textHeight := textBox.Height()
+	halfTextHeight := textHeight >> 1
+
+	pt := style.Padding.GetTop(DefaultAnnotationPadding.Top)
+	pl := style.Padding.GetLeft(DefaultAnnotationPadding.Left)
+	pr := style.Padding.GetRight(DefaultAnnotationPadding.Right)
+	pb := style.Padding.GetBottom(DefaultAnnotationPadding.Bottom)
+
+	strokeWidth := style.GetStrokeWidth()
+
+	top := ly - (pt + halfTextHeight)
+	right := lx + pl + pr + textWidth + DefaultAnnotationDeltaWidth + int(strokeWidth)
+	bottom := ly + (pb + halfTextHeight)
+
+	return Box{
+		Top:    top,
+		Left:   lx,
+		Right:  right,
+		Bottom: bottom,
+	}
+}
+
+// Annotation draws an anotation with a renderer.
+func (d draw) Annotation(r Renderer, canvasBox Box, style Style, lx, ly int, label string) {
+	style.WriteToRenderer(r)
+
+	textBox := r.MeasureText(label)
+	textWidth := textBox.Width()
+	halfTextHeight := textBox.Height() >> 1
+
+	pt := style.Padding.GetTop(DefaultAnnotationPadding.Top)
+	pl := style.Padding.GetLeft(DefaultAnnotationPadding.Left)
+	pr := style.Padding.GetRight(DefaultAnnotationPadding.Right)
+	pb := style.Padding.GetBottom(DefaultAnnotationPadding.Bottom)
+
+	textX := lx + pl + DefaultAnnotationDeltaWidth
+	textY := ly + halfTextHeight
+
+	ltx := lx + DefaultAnnotationDeltaWidth
+	lty := ly - (pt + halfTextHeight)
+
+	rtx := lx + pl + pr + textWidth + DefaultAnnotationDeltaWidth
+	rty := ly - (pt + halfTextHeight)
+
+	rbx := lx + pl + pr + textWidth + DefaultAnnotationDeltaWidth
+	rby := ly + (pb + halfTextHeight)
+
+	lbx := lx + DefaultAnnotationDeltaWidth
+	lby := ly + (pb + halfTextHeight)
+
+	r.MoveTo(lx, ly)
+	r.LineTo(ltx, lty)
+	r.LineTo(rtx, rty)
+	r.LineTo(rbx, rby)
+	r.LineTo(lbx, lby)
+	r.LineTo(lx, ly)
+	r.Close()
+	r.FillStroke()
+
+	r.Text(label, textX, textY)
+}
+
+// Box draws a box with a given style.
+func (d draw) Box(r Renderer, b Box, s Style) {
+	s.WriteToRenderer(r)
+
+	r.MoveTo(b.Left, b.Top)
+	r.LineTo(b.Right, b.Top)
+	r.LineTo(b.Right, b.Bottom)
+	r.LineTo(b.Left, b.Bottom)
+	r.LineTo(b.Left, b.Top)
+	r.FillStroke()
+}
+
+// DrawText draws text with a given style.
+func (d draw) Text(r Renderer, text string, x, y int, style Style) {
+	style.GetTextOptions().WriteToRenderer(r)
+	r.Text(text, x, y)
+}
+
+// TextWithin draws the text within a given box.
+func (d draw) TextWithin(r Renderer, text string, box Box, style Style) {
+	lines := Text.WrapFit(r, text, box.Width(), style)
+	linesBox := Text.MeasureLines(r, lines, style)
+
+	style.GetTextOptions().WriteToRenderer(r)
+
+	y := box.Top
+
+	switch style.GetTextVerticalAlign() {
+	case TextVerticalAlignBottom, TextVerticalAlignBaseline: // i have to build better baseline handling into measure text
+		y = y - linesBox.Height()
+	case TextVerticalAlignMiddle, TextVerticalAlignMiddleBaseline:
+		y = (y - linesBox.Height()) >> 1
+	}
+
+	var tx, ty int
+	for _, line := range lines {
+		lineBox := r.MeasureText(line)
+		switch style.GetTextHorizontalAlign() {
+		case TextHorizontalAlignCenter:
+			tx = box.Left + ((box.Width() - lineBox.Width()) >> 1)
+		case TextHorizontalAlignRight:
+			tx = box.Right - lineBox.Width()
+		default:
+			tx = box.Left
+		}
+		ty = y + lineBox.Height()
+
+		d.Text(r, line, tx, ty, style)
+		y += lineBox.Height() + style.GetTextLineSpacing()
+	}
+}

drawing/path.go

@@ -101,10 +101,10 @@ func (p *Path) CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64) {
 }
 
 // ArcTo adds an arc to the path
-func (p *Path) ArcTo(cx, cy, rx, ry, startAngle, angle float64) {
+func (p *Path) ArcTo(cx, cy, rx, ry, startAngle, delta float64) {
-	endAngle := startAngle + angle
+	endAngle := startAngle + delta
 	clockWise := true
-	if angle < 0 {
+	if delta < 0 {
 		clockWise = false
 	}
 	// normalize
@@ -124,7 +124,7 @@ func (p *Path) ArcTo(cx, cy, rx, ry, startAngle, angle float64) {
 	} else {
 		p.MoveTo(startX, startY)
 	}
-	p.appendToPath(ArcToComponent, cx, cy, rx, ry, startAngle, angle)
+	p.appendToPath(ArcToComponent, cx, cy, rx, ry, startAngle, delta)
 	p.x = cx + math.Cos(endAngle)*rx
 	p.y = cy + math.Sin(endAngle)*ry
 }

drawing/stack_graphic_context.go

@@ -171,8 +171,8 @@ func (gc *StackGraphicContext) CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64) {
 }
 
 // ArcTo draws an arc.
-func (gc *StackGraphicContext) ArcTo(cx, cy, rx, ry, startAngle, angle float64) {
+func (gc *StackGraphicContext) ArcTo(cx, cy, rx, ry, startAngle, delta float64) {
-	gc.current.Path.ArcTo(cx, cy, rx, ry, startAngle, angle)
+	gc.current.Path.ArcTo(cx, cy, rx, ry, startAngle, delta)
 }
 
 // Close closes a path.

drawing/text.go

@@ -1,6 +1,3 @@
-// Copyright 2010 The draw2d Authors. All rights reserved.
-// created: 13/12/2010 by Laurent Le Goff
-
 package drawing
 
 import (

drawing_helpers.go

@@ -1,372 +0,0 @@
-package chart
-
-import (
-	"math"
-
-	"github.com/wcharczuk/go-chart/drawing"
-)
-
-// DrawLineSeries draws a line series with a renderer.
-func DrawLineSeries(r Renderer, canvasBox Box, xrange, yrange Range, s Style, vs ValueProvider) {
-	if vs.Len() == 0 {
-		return
-	}
-
-	cb := canvasBox.Bottom
-	cl := canvasBox.Left
-
-	v0x, v0y := vs.GetValue(0)
-	x0 := cl + xrange.Translate(v0x)
-	y0 := cb - yrange.Translate(v0y)
-
-	var vx, vy float64
-	var x, y int
-
-	fill := s.GetFillColor()
-	if !fill.IsZero() {
-		r.SetFillColor(fill)
-		r.MoveTo(x0, y0)
-		for i := 1; i < vs.Len(); i++ {
-			vx, vy = vs.GetValue(i)
-			x = cl + xrange.Translate(vx)
-			y = cb - yrange.Translate(vy)
-			r.LineTo(x, y)
-		}
-		r.LineTo(x, cb)
-		r.LineTo(x0, cb)
-		r.Close()
-		r.Fill()
-	}
-
-	r.SetStrokeColor(s.GetStrokeColor())
-	r.SetStrokeDashArray(s.GetStrokeDashArray())
-	r.SetStrokeWidth(s.GetStrokeWidth(DefaultStrokeWidth))
-
-	r.MoveTo(x0, y0)
-	for i := 1; i < vs.Len(); i++ {
-		vx, vy = vs.GetValue(i)
-		x = cl + xrange.Translate(vx)
-		y = cb - yrange.Translate(vy)
-		r.LineTo(x, y)
-	}
-	r.Stroke()
-}
-
-// DrawBoundedSeries draws a series that implements BoundedValueProvider.
-func DrawBoundedSeries(r Renderer, canvasBox Box, xrange, yrange Range, s Style, bbs BoundedValueProvider, drawOffsetIndexes ...int) {
-	drawOffsetIndex := 0
-	if len(drawOffsetIndexes) > 0 {
-		drawOffsetIndex = drawOffsetIndexes[0]
-	}
-
-	r.SetStrokeColor(s.GetStrokeColor())
-	r.SetStrokeDashArray(s.GetStrokeDashArray())
-	r.SetStrokeWidth(s.GetStrokeWidth())
-	r.SetFillColor(s.GetFillColor())
-
-	cb := canvasBox.Bottom
-	cl := canvasBox.Left
-
-	v0x, v0y1, v0y2 := bbs.GetBoundedValue(0)
-	x0 := cl + xrange.Translate(v0x)
-	y0 := cb - yrange.Translate(v0y1)
-
-	var vx, vy1, vy2 float64
-	var x, y int
-
-	xvalues := make([]float64, bbs.Len())
-	xvalues[0] = v0x
-	y2values := make([]float64, bbs.Len())
-	y2values[0] = v0y2
-
-	r.MoveTo(x0, y0)
-	for i := 1; i < bbs.Len(); i++ {
-		vx, vy1, vy2 = bbs.GetBoundedValue(i)
-
-		xvalues[i] = vx
-		y2values[i] = vy2
-
-		x = cl + xrange.Translate(vx)
-		y = cb - yrange.Translate(vy1)
-		if i > drawOffsetIndex {
-			r.LineTo(x, y)
-		} else {
-			r.MoveTo(x, y)
-		}
-	}
-	y = cb - yrange.Translate(vy2)
-	r.LineTo(x, y)
-	for i := bbs.Len() - 1; i >= drawOffsetIndex; i-- {
-		vx, vy2 = xvalues[i], y2values[i]
-		x = cl + xrange.Translate(vx)
-		y = cb - yrange.Translate(vy2)
-		r.LineTo(x, y)
-	}
-	r.Close()
-	r.FillStroke()
-}
-
-// DrawHistogramSeries draws a value provider as boxes from 0.
-func DrawHistogramSeries(r Renderer, canvasBox Box, xrange, yrange Range, s Style, vs ValueProvider, barWidths ...int) {
-	if vs.Len() == 0 {
-		return
-	}
-
-	//calculate bar width?
-	seriesLength := vs.Len()
-	barWidth := int(math.Floor(float64(xrange.Domain) / float64(seriesLength)))
-	if len(barWidths) > 0 {
-		barWidth = barWidths[0]
-	}
-
-	cb := canvasBox.Bottom
-	cl := canvasBox.Left
-
-	//foreach datapoint, draw a box.
-	for index := 0; index < seriesLength; index++ {
-		vx, vy := vs.GetValue(index)
-		y0 := yrange.Translate(0)
-		x := cl + xrange.Translate(vx)
-		y := yrange.Translate(vy)
-
-		DrawBox(r, Box{
-			Top:    cb - y0,
-			Left:   x - (barWidth >> 1),
-			Right:  x + (barWidth >> 1),
-			Bottom: cb - y,
-		}, s)
-	}
-}
-
-// MeasureAnnotation measures how big an annotation would be.
-func MeasureAnnotation(r Renderer, canvasBox Box, s Style, lx, ly int, label string) Box {
-	r.SetFillColor(s.GetFillColor(DefaultAnnotationFillColor))
-	r.SetStrokeColor(s.GetStrokeColor())
-	r.SetStrokeWidth(s.GetStrokeWidth())
-	r.SetFont(s.GetFont())
-	r.SetFontColor(s.GetFontColor(DefaultTextColor))
-	r.SetFontSize(s.GetFontSize(DefaultAnnotationFontSize))
-
-	textBox := r.MeasureText(label)
-	textWidth := textBox.Width()
-	textHeight := textBox.Height()
-	halfTextHeight := textHeight >> 1
-
-	pt := s.Padding.GetTop(DefaultAnnotationPadding.Top)
-	pl := s.Padding.GetLeft(DefaultAnnotationPadding.Left)
-	pr := s.Padding.GetRight(DefaultAnnotationPadding.Right)
-	pb := s.Padding.GetBottom(DefaultAnnotationPadding.Bottom)
-
-	strokeWidth := s.GetStrokeWidth()
-
-	top := ly - (pt + halfTextHeight)
-	right := lx + pl + pr + textWidth + DefaultAnnotationDeltaWidth + int(strokeWidth)
-	bottom := ly + (pb + halfTextHeight)
-
-	return Box{
-		Top:    top,
-		Left:   lx,
-		Right:  right,
-		Bottom: bottom,
-	}
-}
-
-// DrawAnnotation draws an anotation with a renderer.
-func DrawAnnotation(r Renderer, canvasBox Box, style Style, lx, ly int, label string) {
-	r.SetFillColor(style.GetFillColor())
-	r.SetStrokeColor(style.GetStrokeColor())
-	r.SetStrokeWidth(style.GetStrokeWidth())
-	r.SetStrokeDashArray(style.GetStrokeDashArray())
-
-	r.SetFont(style.GetFont())
-	r.SetFontColor(style.GetFontColor(DefaultTextColor))
-	r.SetFontSize(style.GetFontSize(DefaultAnnotationFontSize))
-
-	textBox := r.MeasureText(label)
-	textWidth := textBox.Width()
-	halfTextHeight := textBox.Height() >> 1
-
-	pt := style.Padding.GetTop(DefaultAnnotationPadding.Top)
-	pl := style.Padding.GetLeft(DefaultAnnotationPadding.Left)
-	pr := style.Padding.GetRight(DefaultAnnotationPadding.Right)
-	pb := style.Padding.GetBottom(DefaultAnnotationPadding.Bottom)
-
-	textX := lx + pl + DefaultAnnotationDeltaWidth
-	textY := ly + halfTextHeight
-
-	ltx := lx + DefaultAnnotationDeltaWidth
-	lty := ly - (pt + halfTextHeight)
-
-	rtx := lx + pl + pr + textWidth + DefaultAnnotationDeltaWidth
-	rty := ly - (pt + halfTextHeight)
-
-	rbx := lx + pl + pr + textWidth + DefaultAnnotationDeltaWidth
-	rby := ly + (pb + halfTextHeight)
-
-	lbx := lx + DefaultAnnotationDeltaWidth
-	lby := ly + (pb + halfTextHeight)
-
-	r.MoveTo(lx, ly)
-	r.LineTo(ltx, lty)
-	r.LineTo(rtx, rty)
-	r.LineTo(rbx, rby)
-	r.LineTo(lbx, lby)
-	r.LineTo(lx, ly)
-	r.Close()
-	r.FillStroke()
-
-	r.Text(label, textX, textY)
-}
-
-// DrawBox draws a box with a given style.
-func DrawBox(r Renderer, b Box, s Style) {
-	r.SetFillColor(s.GetFillColor())
-	r.SetStrokeColor(s.GetStrokeColor())
-	r.SetStrokeWidth(s.GetStrokeWidth(DefaultStrokeWidth))
-	r.SetStrokeDashArray(s.GetStrokeDashArray())
-
-	r.MoveTo(b.Left, b.Top)
-	r.LineTo(b.Right, b.Top)
-	r.LineTo(b.Right, b.Bottom)
-	r.LineTo(b.Left, b.Bottom)
-	r.LineTo(b.Left, b.Top)
-	r.FillStroke()
-}
-
-// DrawText draws text with a given style.
-func DrawText(r Renderer, text string, x, y int, s Style) {
-	r.SetFontColor(s.GetFontColor(DefaultTextColor))
-	r.SetStrokeColor(s.GetStrokeColor())
-	r.SetStrokeWidth(s.GetStrokeWidth())
-	r.SetFont(s.GetFont())
-	r.SetFontSize(s.GetFontSize())
-
-	r.Text(text, x, y)
-}
-
-// DrawTextCentered draws text with a given style centered.
-func DrawTextCentered(r Renderer, text string, x, y int, s Style) {
-	r.SetFontColor(s.GetFontColor(DefaultTextColor))
-	r.SetStrokeColor(s.GetStrokeColor())
-	r.SetStrokeWidth(s.GetStrokeWidth())
-	r.SetFont(s.GetFont())
-	r.SetFontSize(s.GetFontSize())
-
-	tb := r.MeasureText(text)
-	tx := x - (tb.Width() >> 1)
-	ty := y - (tb.Height() >> 1)
-	r.Text(text, tx, ty)
-}
-
-// CreateLegend returns a legend renderable function.
-func CreateLegend(c *Chart, userDefaults ...Style) Renderable {
-	return func(r Renderer, cb Box, chartDefaults Style) {
-		legendDefaults := Style{
-			FillColor:   drawing.ColorWhite,
-			FontColor:   DefaultTextColor,
-			FontSize:    8.0,
-			StrokeColor: DefaultAxisColor,
-			StrokeWidth: DefaultAxisLineWidth,
-		}
-
-		var legendStyle Style
-		if len(userDefaults) > 0 {
-			legendStyle = userDefaults[0].WithDefaultsFrom(chartDefaults.WithDefaultsFrom(legendDefaults))
-		} else {
-			legendStyle = chartDefaults.WithDefaultsFrom(legendDefaults)
-		}
-
-		// DEFAULTS
-		legendPadding := Box{
-			Top:    5,
-			Left:   5,
-			Right:  5,
-			Bottom: 5,
-		}
-		lineTextGap := 5
-		lineLengthMinimum := 25
-
-		var labels []string
-		var lines []Style
-		for index, s := range c.Series {
-			if s.GetStyle().IsZero() || s.GetStyle().Show {
-				if _, isAnnotationSeries := s.(AnnotationSeries); !isAnnotationSeries {
-					labels = append(labels, s.GetName())
-					lines = append(lines, s.GetStyle().WithDefaultsFrom(c.styleDefaultsSeries(index)))
-				}
-			}
-		}
-
-		legend := Box{
-			Top:  cb.Top,
-			Left: cb.Left,
-			// bottom and right will be sized by the legend content + relevant padding.
-		}
-
-		legendContent := Box{
-			Top:    legend.Top + legendPadding.Top,
-			Left:   legend.Left + legendPadding.Left,
-			Right:  legend.Left + legendPadding.Left,
-			Bottom: legend.Top + legendPadding.Top,
-		}
-
-		r.SetFont(legendStyle.GetFont())
-		r.SetFontColor(legendStyle.GetFontColor())
-		r.SetFontSize(legendStyle.GetFontSize())
-
-		// measure
-		labelCount := 0
-		for x := 0; x < len(labels); x++ {
-			if len(labels[x]) > 0 {
-				tb := r.MeasureText(labels[x])
-				if labelCount > 0 {
-					legendContent.Bottom += DefaultMinimumTickVerticalSpacing
-				}
-				legendContent.Bottom += tb.Height()
-				right := legendContent.Left + tb.Width() + lineTextGap + lineLengthMinimum
-				legendContent.Right = MaxInt(legendContent.Right, right)
-				labelCount++
-			}
-		}
-
-		legend = legend.Grow(legendContent)
-		legend.Right = legendContent.Right + legendPadding.Right
-		legend.Bottom = legendContent.Bottom + legendPadding.Bottom
-
-		DrawBox(r, legend, legendStyle)
-
-		ycursor := legendContent.Top
-		tx := legendContent.Left
-		legendCount := 0
-		for x := 0; x < len(labels); x++ {
-			if len(labels[x]) > 0 {
-
-				if legendCount > 0 {
-					ycursor += DefaultMinimumTickVerticalSpacing
-				}
-
-				tb := r.MeasureText(labels[x])
-
-				ty := ycursor + tb.Height()
-				r.Text(labels[x], tx, ty)
-
-				th2 := tb.Height() >> 1
-
-				lx := tx + tb.Width() + lineTextGap
-				ly := ty - th2
-				lx2 := legendContent.Right - legendPadding.Right
-
-				r.SetStrokeColor(lines[x].GetStrokeColor())
-				r.SetStrokeWidth(lines[x].GetStrokeWidth())
-				r.SetStrokeDashArray(lines[x].GetStrokeDashArray())
-
-				r.MoveTo(lx, ly)
-				r.LineTo(lx2, ly)
-				r.Stroke()
-
-				ycursor += tb.Height()
-				legendCount++
-			}
-		}
-	}
-}

ema_series.go

@@ -9,7 +9,7 @@ const (
 type EMASeries struct {
 	Name  string
 	Style Style
-	YAxis YAxisType
+	YAxis yAxisType
 
 	Period      int
 	InnerSeries ValueProvider
@@ -28,7 +28,7 @@ func (ema EMASeries) GetStyle() Style {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (ema EMASeries) GetYAxis() YAxisType {
+func (ema EMASeries) GetYAxis() yAxisType {
 	return ema.YAxis
 }
 
@@ -96,6 +96,6 @@ func (ema *EMASeries) ensureCachedValues() {
 
 // Render renders the series.
 func (ema *EMASeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	style := ema.Style.WithDefaultsFrom(defaults)
+	style := ema.Style.InheritFrom(defaults)
-	DrawLineSeries(r, canvasBox, xrange, yrange, style, ema)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, ema)
 }

ema_series_test.go

@@ -7,7 +7,7 @@ import (
 )
 
 var (
-	emaXValues = Seq(1.0, 50.0)
+	emaXValues = Sequence.Float64(1.0, 50.0)
 	emaYValues = []float64{
 		1, 2, 3, 4, 5, 4, 3, 2,
 		1, 2, 3, 4, 5, 4, 3, 2,

examples/annotations/main.go

@@ -26,12 +26,12 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
 			},
 			chart.AnnotationSeries{
-				Annotations: []chart.Annotation{
+				Annotations: []chart.Value2{
-					{X: 1.0, Y: 1.0, Label: "One"},
+					{XValue: 1.0, YValue: 1.0, Label: "One"},
-					{X: 2.0, Y: 2.0, Label: "Two"},
+					{XValue: 2.0, YValue: 2.0, Label: "Two"},
-					{X: 3.0, Y: 3.0, Label: "Three"},
+					{XValue: 3.0, YValue: 3.0, Label: "Three"},
-					{X: 4.0, Y: 4.0, Label: "Four"},
+					{XValue: 4.0, YValue: 4.0, Label: "Four"},
-					{X: 5.0, Y: 5.0, Label: "Five"},
+					{XValue: 5.0, YValue: 5.0, Label: "Five"},
 				},
 			},
 		},

examples/axes/main.go

@@ -28,8 +28,8 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 			chart.ContinuousSeries{
 				Style: chart.Style{
 					Show:        true,
-					StrokeColor: chart.GetDefaultSeriesStrokeColor(0).WithAlpha(64),
+					StrokeColor: chart.GetDefaultColor(0).WithAlpha(64),
-					FillColor:   chart.GetDefaultSeriesStrokeColor(0).WithAlpha(64),
+					FillColor:   chart.GetDefaultColor(0).WithAlpha(64),
 				},
 				XValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},
 				YValues: []float64{1.0, 2.0, 3.0, 4.0, 5.0},

examples/custom_padding/main.go

@@ -30,8 +30,8 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 		},
 		Series: []chart.Series{
 			chart.ContinuousSeries{
-				XValues: chart.Seq(1.0, 100.0),
+				XValues: chart.Sequence.Float64(1.0, 100.0),
-				YValues: chart.SeqRand(100.0, 256.0),
+				YValues: chart.Sequence.Random(100.0, 256.0),
 			},
 		},
 	}
@@ -57,8 +57,8 @@ func drawChartDefault(res http.ResponseWriter, req *http.Request) {
 		},
 		Series: []chart.Series{
 			chart.ContinuousSeries{
-				XValues: chart.Seq(1.0, 100.0),
+				XValues: chart.Sequence.Float64(1.0, 100.0),
-				YValues: chart.SeqRand(100.0, 256.0),
+				YValues: chart.Sequence.Random(100.0, 256.0),
 			},
 		},
 	}

examples/custom_ranges/main.go

@@ -17,7 +17,7 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 			Style: chart.Style{
 				Show: true,
 			},
-			Range: chart.Range{
+			Range: &chart.ContinuousRange{
 				Min: 0.0,
 				Max: 10.0,
 			},

examples/custom_ticks/main.go

@@ -17,7 +17,7 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 			Style: chart.Style{
 				Show: true,
 			},
-			Range: chart.Range{
+			Range: &chart.ContinuousRange{
 				Min: 0.0,
 				Max: 4.0,
 			},

examples/legend/main.go

@@ -38,7 +38,7 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 
 	//note we have to do this as a separate step because we need a reference to graph
 	graph.Elements = []chart.Renderable{
-		chart.CreateLegend(&graph),
+		chart.Legend(&graph),
 	}
 
 	res.Header().Set("Content-Type", "image/png")

examples/linear_regression/main.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+
+	/*
+		In this example we add a new type of series, a `SimpleMovingAverageSeries` that takes another series as a required argument.
+		InnerSeries only needs to implement `ValueProvider`, so really you could chain `SimpleMovingAverageSeries` together if you wanted.
+	*/
+
+	mainSeries := chart.ContinuousSeries{
+		Name:    "A test series",
+		XValues: chart.Sequence.Float64(1.0, 100.0), //generates a []float64 from 1.0 to 100.0 in 1.0 step increments, or 100 elements.
+		YValues: chart.Sequence.Random(100, 100),    //generates a []float64 randomly from 0 to 100 with 100 elements.
+	}
+
+	// note we create a LinearRegressionSeries series by assignin the inner series.
+	// we need to use a reference because `.Render()` needs to modify state within the series.
+	linRegSeries := &chart.LinearRegressionSeries{
+		InnerSeries: mainSeries,
+	} // we can optionally set the `WindowSize` property which alters how the moving average is calculated.
+
+	graph := chart.Chart{
+		Series: []chart.Series{
+			mainSeries,
+			linRegSeries,
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	graph.Render(chart.PNG, res)
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	http.ListenAndServe(":8080", nil)
+}

examples/pie_chart/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+	pie := chart.PieChart{
+		Title: "test\nchart",
+		TitleStyle: chart.Style{
+			Show: true,
+		},
+		Width:  512,
+		Height: 512,
+		Values: []chart.Value{
+			{Value: 5, Label: "Blue"},
+			{Value: 5, Label: "Green"},
+			{Value: 4, Label: "Gray"},
+			{Value: 4, Label: "Orange"},
+			{Value: 3, Label: "Test"},
+			{Value: 3, Label: "??"},
+			{Value: 1, Label: "!!"},
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	err := pie.Render(chart.PNG, res)
+	if err != nil {
+		fmt.Printf("Error rendering pie chart: %v\n", err)
+	}
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}

examples/simple_moving_average/main.go

@@ -15,8 +15,8 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 
 	mainSeries := chart.ContinuousSeries{
 		Name:    "A test series",
-		XValues: chart.Seq(1.0, 100.0),   //generates a []float64 from 1.0 to 100.0 in 1.0 step increments, or 100 elements.
+		XValues: chart.Sequence.Float64(1.0, 100.0), //generates a []float64 from 1.0 to 100.0 in 1.0 step increments, or 100 elements.
-		YValues: chart.SeqRand(100, 100), //generates a []float64 randomly from 0 to 100 with 100 elements.
+		YValues: chart.Sequence.Random(100, 100),    //generates a []float64 randomly from 0 to 100 with 100 elements.
 	}
 
 	// note we create a SimpleMovingAverage series by assignin the inner series.

examples/stacked_bar/main.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+	sbc := chart.StackedBarChart{
+		Height: 512,
+		XAxis: chart.Style{
+			Show: true,
+		},
+		YAxis: chart.Style{
+			Show: true,
+		},
+		Bars: []chart.StackedBar{
+			{
+				Name: "This is a very long string to test word break wrapping.",
+				Values: []chart.Value{
+					{Value: 5, Label: "Blue"},
+					{Value: 5, Label: "Green"},
+					{Value: 4, Label: "Gray"},
+					{Value: 3, Label: "Orange"},
+					{Value: 3, Label: "Test"},
+					{Value: 2, Label: "??"},
+					{Value: 1, Label: "!!"},
+				},
+			},
+			{
+				Name: "Test",
+				Values: []chart.Value{
+					{Value: 10, Label: "Blue"},
+					{Value: 5, Label: "Green"},
+					{Value: 1, Label: "Gray"},
+				},
+			},
+			{
+				Name: "Test 2",
+				Values: []chart.Value{
+					{Value: 10, Label: "Blue"},
+					{Value: 6, Label: "Green"},
+					{Value: 4, Label: "Gray"},
+				},
+			},
+		},
+	}
+
+	res.Header().Set("Content-Type", "image/png")
+	err := sbc.Render(chart.PNG, res)
+	if err != nil {
+		fmt.Printf("Error rendering chart: %v\n", err)
+	}
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}

examples/stock_analysis/main.go

@@ -15,7 +15,7 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 		Name: "SPY",
 		Style: chart.Style{
 			Show:        true,
-			StrokeColor: chart.GetDefaultSeriesStrokeColor(0),
+			StrokeColor: chart.GetDefaultColor(0),
 		},
 		XValues: xv,
 		YValues: yv,
@@ -43,11 +43,12 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 
 	graph := chart.Chart{
 		XAxis: chart.XAxis{
-			Style: chart.Style{Show: true},
+			Style:        chart.Style{Show: true},
+			TickPosition: chart.TickPositionBetweenTicks,
 		},
 		YAxis: chart.YAxis{
 			Style: chart.Style{Show: true},
-			Range: chart.Range{
+			Range: &chart.ContinuousRange{
 				Max: 220.0,
 				Min: 180.0,
 			},

grid_line.go

@@ -1,31 +1,8 @@
 package chart
 
-// GenerateGridLines generates grid lines.
+// GridLineProvider is a type that provides grid lines.
-func GenerateGridLines(ticks []Tick, isVertical bool) []GridLine {
+type GridLineProvider interface {
-	var gl []GridLine
+	GetGridLines(ticks []Tick, isVertical bool, majorStyle, minorStyle Style) []GridLine
-	isMinor := false
-	minorStyle := Style{
-		StrokeColor: DefaultGridLineColor.WithAlpha(100),
-		StrokeWidth: 1.0,
-	}
-	majorStyle := Style{
-		StrokeColor: DefaultGridLineColor,
-		StrokeWidth: 1.0,
-	}
-	for _, t := range ticks {
-		s := majorStyle
-		if isMinor {
-			s = minorStyle
-		}
-		gl = append(gl, GridLine{
-			Style:      s,
-			IsMinor:    isMinor,
-			IsVertical: isVertical,
-			Value:      t.Value,
-		})
-		isMinor = !isMinor
-	}
-	return gl
 }
 
 // GridLine is a line on a graph canvas.
@@ -57,15 +34,16 @@ func (gl GridLine) Horizontal() bool {
 }
 
 // Render renders the gridline
-func (gl GridLine) Render(r Renderer, canvasBox Box, ra Range) {
+func (gl GridLine) Render(r Renderer, canvasBox Box, ra Range, defaults Style) {
+	r.SetStrokeColor(gl.Style.GetStrokeColor(defaults.GetStrokeColor()))
+	r.SetStrokeWidth(gl.Style.GetStrokeWidth(defaults.GetStrokeWidth()))
+	r.SetStrokeDashArray(gl.Style.GetStrokeDashArray(defaults.GetStrokeDashArray()))
+
 	if gl.IsVertical {
 		lineLeft := canvasBox.Left + ra.Translate(gl.Value)
 		lineBottom := canvasBox.Bottom
 		lineTop := canvasBox.Top
 
-		r.SetStrokeColor(gl.Style.GetStrokeColor(DefaultAxisColor))
-		r.SetStrokeWidth(gl.Style.GetStrokeWidth(DefaultAxisLineWidth))
-
 		r.MoveTo(lineLeft, lineBottom)
 		r.LineTo(lineLeft, lineTop)
 		r.Stroke()
@@ -74,11 +52,33 @@ func (gl GridLine) Render(r Renderer, canvasBox Box, ra Range) {
 		lineRight := canvasBox.Right
 		lineHeight := canvasBox.Bottom - ra.Translate(gl.Value)
 
-		r.SetStrokeColor(gl.Style.GetStrokeColor(DefaultAxisColor))
-		r.SetStrokeWidth(gl.Style.GetStrokeWidth(DefaultAxisLineWidth))
-
 		r.MoveTo(lineLeft, lineHeight)
 		r.LineTo(lineRight, lineHeight)
 		r.Stroke()
 	}
 }
+
+// GenerateGridLines generates grid lines.
+func GenerateGridLines(ticks []Tick, majorStyle, minorStyle Style, isVertical bool) []GridLine {
+	var gl []GridLine
+	isMinor := false
+
+	if len(ticks) < 3 {
+		return gl
+	}
+
+	for _, t := range ticks[1 : len(ticks)-1] {
+		s := majorStyle
+		if isMinor {
+			s = minorStyle
+		}
+		gl = append(gl, GridLine{
+			Style:      s,
+			IsMinor:    isMinor,
+			IsVertical: isVertical,
+			Value:      t.Value,
+		})
+		isMinor = !isMinor
+	}
+	return gl
+}

grid_line_test.go

@@ -16,12 +16,11 @@ func TestGenerateGridLines(t *testing.T) {
 		{Value: 4.0, Label: "4.0"},
 	}
 
-	gl := GenerateGridLines(ticks, true)
+	gl := GenerateGridLines(ticks, Style{}, Style{}, true)
-	assert.Len(gl, 4)
+	assert.Len(gl, 2)
-	assert.Equal(1.0, gl[0].Value)
+
-	assert.Equal(2.0, gl[1].Value)
+	assert.Equal(2.0, gl[0].Value)
-	assert.Equal(3.0, gl[2].Value)
+	assert.Equal(3.0, gl[1].Value)
-	assert.Equal(4.0, gl[3].Value)
 
 	assert.True(gl[0].IsVertical)
 }

histogram_series.go

@@ -6,7 +6,7 @@ package chart
 type HistogramSeries struct {
 	Name        string
 	Style       Style
-	YAxis       YAxisType
+	YAxis       yAxisType
 	InnerSeries ValueProvider
 }
 
@@ -21,7 +21,7 @@ func (hs HistogramSeries) GetStyle() Style {
 }
 
 // GetYAxis returns which yaxis the series is mapped to.
-func (hs HistogramSeries) GetYAxis() YAxisType {
+func (hs HistogramSeries) GetYAxis() yAxisType {
 	return hs.YAxis
 }
 
@@ -52,6 +52,6 @@ func (hs HistogramSeries) GetBoundedValue(index int) (x, y1, y2 float64) {
 
 // Render implements Series.Render.
 func (hs HistogramSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	style := hs.Style.WithDefaultsFrom(defaults)
+	style := hs.Style.InheritFrom(defaults)
-	DrawHistogramSeries(r, canvasBox, xrange, yrange, style, hs)
+	Draw.HistogramSeries(r, canvasBox, xrange, yrange, style, hs)
 }

histogram_series_test.go

@@ -0,0 +1,31 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestHistogramSeries(t *testing.T) {
+	assert := assert.New(t)
+
+	cs := ContinuousSeries{
+		Name:    "Test Series",
+		XValues: Sequence.Float64(1.0, 20.0),
+		YValues: Sequence.Float64(10.0, -10.0),
+	}
+
+	hs := HistogramSeries{
+		InnerSeries: cs,
+	}
+
+	for x := 0; x < hs.Len(); x++ {
+		csx, csy := cs.GetValue(0)
+		hsx, hsy1, hsy2 := hs.GetBoundedValue(0)
+		assert.Equal(csx, hsx)
+		assert.True(hsy1 > 0)
+		assert.True(hsy2 <= 0)
+		assert.True(csy < 0 || (csy > 0 && csy == hsy1))
+		assert.True(csy > 0 || (csy < 0 && csy == hsy2))
+	}
+}

legend.go

@@ -0,0 +1,116 @@
+package chart
+
+import "github.com/wcharczuk/go-chart/drawing"
+
+// Legend returns a legend renderable function.
+func Legend(c *Chart, userDefaults ...Style) Renderable {
+	return func(r Renderer, cb Box, chartDefaults Style) {
+		legendDefaults := Style{
+			FillColor:   drawing.ColorWhite,
+			FontColor:   DefaultTextColor,
+			FontSize:    8.0,
+			StrokeColor: DefaultAxisColor,
+			StrokeWidth: DefaultAxisLineWidth,
+		}
+
+		var legendStyle Style
+		if len(userDefaults) > 0 {
+			legendStyle = userDefaults[0].InheritFrom(chartDefaults.InheritFrom(legendDefaults))
+		} else {
+			legendStyle = chartDefaults.InheritFrom(legendDefaults)
+		}
+
+		// DEFAULTS
+		legendPadding := Box{
+			Top:    5,
+			Left:   5,
+			Right:  5,
+			Bottom: 5,
+		}
+		lineTextGap := 5
+		lineLengthMinimum := 25
+
+		var labels []string
+		var lines []Style
+		for index, s := range c.Series {
+			if s.GetStyle().IsZero() || s.GetStyle().Show {
+				if _, isAnnotationSeries := s.(AnnotationSeries); !isAnnotationSeries {
+					labels = append(labels, s.GetName())
+					lines = append(lines, s.GetStyle().InheritFrom(c.styleDefaultsSeries(index)))
+				}
+			}
+		}
+
+		legend := Box{
+			Top:  cb.Top,
+			Left: cb.Left,
+			// bottom and right will be sized by the legend content + relevant padding.
+		}
+
+		legendContent := Box{
+			Top:    legend.Top + legendPadding.Top,
+			Left:   legend.Left + legendPadding.Left,
+			Right:  legend.Left + legendPadding.Left,
+			Bottom: legend.Top + legendPadding.Top,
+		}
+
+		r.SetFont(legendStyle.GetFont())
+		r.SetFontColor(legendStyle.GetFontColor())
+		r.SetFontSize(legendStyle.GetFontSize())
+
+		// measure
+		labelCount := 0
+		for x := 0; x < len(labels); x++ {
+			if len(labels[x]) > 0 {
+				tb := r.MeasureText(labels[x])
+				if labelCount > 0 {
+					legendContent.Bottom += DefaultMinimumTickVerticalSpacing
+				}
+				legendContent.Bottom += tb.Height()
+				right := legendContent.Left + tb.Width() + lineTextGap + lineLengthMinimum
+				legendContent.Right = Math.MaxInt(legendContent.Right, right)
+				labelCount++
+			}
+		}
+
+		legend = legend.Grow(legendContent)
+		legend.Right = legendContent.Right + legendPadding.Right
+		legend.Bottom = legendContent.Bottom + legendPadding.Bottom
+
+		Draw.Box(r, legend, legendStyle)
+
+		ycursor := legendContent.Top
+		tx := legendContent.Left
+		legendCount := 0
+		for x := 0; x < len(labels); x++ {
+			if len(labels[x]) > 0 {
+
+				if legendCount > 0 {
+					ycursor += DefaultMinimumTickVerticalSpacing
+				}
+
+				tb := r.MeasureText(labels[x])
+
+				ty := ycursor + tb.Height()
+				r.Text(labels[x], tx, ty)
+
+				th2 := tb.Height() >> 1
+
+				lx := tx + tb.Width() + lineTextGap
+				ly := ty - th2
+				lx2 := legendContent.Right - legendPadding.Right
+
+				r.SetStrokeColor(lines[x].GetStrokeColor())
+				r.SetStrokeWidth(lines[x].GetStrokeWidth())
+				r.SetStrokeDashArray(lines[x].GetStrokeDashArray())
+
+				r.MoveTo(lx, ly)
+				r.LineTo(lx2, ly)
+				r.Stroke()
+
+				ycursor += tb.Height()
+				legendCount++
+			}
+		}
+	}
+}

linear_regression_series.go

@@ -0,0 +1,132 @@
+package chart
+
+// LinearRegressionSeries is a series that plots the n-nearest neighbors
+// linear regression for the values.
+type LinearRegressionSeries struct {
+	Name  string
+	Style Style
+	YAxis yAxisType
+
+	Window      int
+	Offset      int
+	InnerSeries ValueProvider
+
+	m       float64
+	b       float64
+	avgx    float64
+	stddevx float64
+}
+
+// GetName returns the name of the time series.
+func (lrs LinearRegressionSeries) GetName() string {
+	return lrs.Name
+}
+
+// GetStyle returns the line style.
+func (lrs LinearRegressionSeries) GetStyle() Style {
+	return lrs.Style
+}
+
+// GetYAxis returns which YAxis the series draws on.
+func (lrs LinearRegressionSeries) GetYAxis() yAxisType {
+	return lrs.YAxis
+}
+
+// Len returns the number of elements in the series.
+func (lrs LinearRegressionSeries) Len() int {
+	return Math.MinInt(lrs.GetWindow(), lrs.InnerSeries.Len()-lrs.GetOffset())
+}
+
+// GetWindow returns the window size.
+func (lrs LinearRegressionSeries) GetWindow() int {
+	if lrs.Window == 0 {
+		return lrs.InnerSeries.Len()
+	}
+	return lrs.Window
+}
+
+// GetEndIndex returns the effective window end.
+func (lrs LinearRegressionSeries) GetEndIndex() int {
+	return Math.MinInt(lrs.GetOffset()+(lrs.Len()), (lrs.InnerSeries.Len() - 1))
+}
+
+// GetOffset returns the data offset.
+func (lrs LinearRegressionSeries) GetOffset() int {
+	if lrs.Offset == 0 {
+		return 0
+	}
+	return lrs.Offset
+}
+
+// GetValue gets a value at a given index.
+func (lrs *LinearRegressionSeries) GetValue(index int) (x, y float64) {
+	if lrs.InnerSeries == nil {
+		return
+	}
+	if lrs.m == 0 && lrs.b == 0 {
+		lrs.computeCoefficients()
+	}
+	offset := lrs.GetOffset()
+	effectiveIndex := Math.MinInt(index+offset, lrs.InnerSeries.Len())
+	x, y = lrs.InnerSeries.GetValue(effectiveIndex)
+	y = (lrs.m * lrs.normalize(x)) + lrs.b
+	return
+}
+
+// GetLastValue computes the last moving average value but walking back window size samples,
+// and recomputing the last moving average chunk.
+func (lrs *LinearRegressionSeries) GetLastValue() (x, y float64) {
+	if lrs.InnerSeries == nil {
+		return
+	}
+	if lrs.m == 0 && lrs.b == 0 {
+		lrs.computeCoefficients()
+	}
+	endIndex := lrs.GetEndIndex()
+	x, y = lrs.InnerSeries.GetValue(endIndex)
+	y = (lrs.m * lrs.normalize(x)) + lrs.b
+	return
+}
+
+func (lrs *LinearRegressionSeries) normalize(xvalue float64) float64 {
+	return (xvalue - lrs.avgx) / lrs.stddevx
+}
+
+// computeCoefficients computes the `m` and `b` terms in the linear formula given by `y = mx+b`.
+func (lrs *LinearRegressionSeries) computeCoefficients() {
+	startIndex := lrs.GetOffset()
+	endIndex := lrs.GetEndIndex()
+
+	p := float64(endIndex - startIndex)
+
+	xvalues := NewRingBufferWithCapacity(lrs.Len())
+	for index := startIndex; index < endIndex; index++ {
+
+		x, _ := lrs.InnerSeries.GetValue(index)
+		xvalues.Enqueue(x)
+	}
+
+	lrs.avgx = xvalues.Average()
+	lrs.stddevx = xvalues.StdDev()
+
+	var sumx, sumy, sumxx, sumxy float64
+	for index := startIndex; index < endIndex; index++ {
+		x, y := lrs.InnerSeries.GetValue(index)
+
+		x = lrs.normalize(x)
+
+		sumx += x
+		sumy += y
+		sumxx += x * x
+		sumxy += x * y
+	}
+
+	lrs.m = (p*sumxy - sumx*sumy) / (p*sumxx - sumx*sumx)
+	lrs.b = (sumy / p) - (lrs.m * sumx / p)
+}
+
+// Render renders the series.
+func (lrs *LinearRegressionSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
+	style := lrs.Style.InheritFrom(defaults)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, lrs)
+}

linear_regression_series_test.go

@@ -0,0 +1,77 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestLinearRegressionSeries(t *testing.T) {
+	assert := assert.New(t)
+
+	mainSeries := ContinuousSeries{
+		Name:    "A test series",
+		XValues: Sequence.Float64(1.0, 100.0),
+		YValues: Sequence.Float64(1.0, 100.0),
+	}
+
+	linRegSeries := &LinearRegressionSeries{
+		InnerSeries: mainSeries,
+	}
+
+	lrx0, lry0 := linRegSeries.GetValue(0)
+	assert.InDelta(1.0, lrx0, 0.0000001)
+	assert.InDelta(1.0, lry0, 0.0000001)
+
+	lrxn, lryn := linRegSeries.GetLastValue()
+	assert.InDelta(100.0, lrxn, 0.0000001)
+	assert.InDelta(100.0, lryn, 0.0000001)
+}
+
+func TestLinearRegressionSeriesDesc(t *testing.T) {
+	assert := assert.New(t)
+
+	mainSeries := ContinuousSeries{
+		Name:    "A test series",
+		XValues: Sequence.Float64(100.0, 1.0),
+		YValues: Sequence.Float64(100.0, 1.0),
+	}
+
+	linRegSeries := &LinearRegressionSeries{
+		InnerSeries: mainSeries,
+	}
+
+	lrx0, lry0 := linRegSeries.GetValue(0)
+	assert.InDelta(100.0, lrx0, 0.0000001)
+	assert.InDelta(100.0, lry0, 0.0000001)
+
+	lrxn, lryn := linRegSeries.GetLastValue()
+	assert.InDelta(1.0, lrxn, 0.0000001)
+	assert.InDelta(1.0, lryn, 0.0000001)
+}
+
+func TestLinearRegressionSeriesWindowAndOffset(t *testing.T) {
+	assert := assert.New(t)
+
+	mainSeries := ContinuousSeries{
+		Name:    "A test series",
+		XValues: Sequence.Float64(100.0, 1.0),
+		YValues: Sequence.Float64(100.0, 1.0),
+	}
+
+	linRegSeries := &LinearRegressionSeries{
+		InnerSeries: mainSeries,
+		Offset:      10,
+		Window:      10,
+	}
+
+	assert.Equal(10, linRegSeries.Len())
+
+	lrx0, lry0 := linRegSeries.GetValue(0)
+	assert.InDelta(90.0, lrx0, 0.0000001)
+	assert.InDelta(90.0, lry0, 0.0000001)
+
+	lrxn, lryn := linRegSeries.GetLastValue()
+	assert.InDelta(80.0, lrxn, 0.0000001)
+	assert.InDelta(80.0, lryn, 0.0000001)
+}

macd_series.go

@@ -14,7 +14,7 @@ const (
 type MACDSeries struct {
 	Name        string
 	Style       Style
-	YAxis       YAxisType
+	YAxis       yAxisType
 	InnerSeries ValueProvider
 
 	PrimaryPeriod   int
@@ -56,7 +56,7 @@ func (macd MACDSeries) GetStyle() Style {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (macd MACDSeries) GetYAxis() YAxisType {
+func (macd MACDSeries) GetYAxis() yAxisType {
 	return macd.YAxis
 }
 
@@ -109,7 +109,7 @@ func (macd *MACDSeries) ensureChildSeries() {
 type MACDSignalSeries struct {
 	Name        string
 	Style       Style
-	YAxis       YAxisType
+	YAxis       yAxisType
 	InnerSeries ValueProvider
 
 	PrimaryPeriod   int
@@ -150,7 +150,7 @@ func (macds MACDSignalSeries) GetStyle() Style {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (macds MACDSignalSeries) GetYAxis() YAxisType {
+func (macds MACDSignalSeries) GetYAxis() yAxisType {
 	return macds.YAxis
 }
 
@@ -192,15 +192,15 @@ func (macds *MACDSignalSeries) ensureSignal() {
 
 // Render renders the series.
 func (macds *MACDSignalSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	style := macds.Style.WithDefaultsFrom(defaults)
+	style := macds.Style.InheritFrom(defaults)
-	DrawLineSeries(r, canvasBox, xrange, yrange, style, macds)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, macds)
 }
 
 // MACDLineSeries is a series that computes the inner ema1-ema2 value as a series.
 type MACDLineSeries struct {
 	Name        string
 	Style       Style
-	YAxis       YAxisType
+	YAxis       yAxisType
 	InnerSeries ValueProvider
 
 	PrimaryPeriod   int
@@ -223,7 +223,7 @@ func (macdl MACDLineSeries) GetStyle() Style {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (macdl MACDLineSeries) GetYAxis() YAxisType {
+func (macdl MACDLineSeries) GetYAxis() yAxisType {
 	return macdl.YAxis
 }
 
@@ -284,6 +284,6 @@ func (macdl *MACDLineSeries) ensureEMASeries() {
 
 // Render renders the series.
 func (macdl *MACDLineSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	style := macdl.Style.WithDefaultsFrom(defaults)
+	style := macdl.Style.InheritFrom(defaults)
-	DrawLineSeries(r, canvasBox, xrange, yrange, style, macdl)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, macdl)
 }

market_hours_range.go

@@ -0,0 +1,133 @@
+package chart
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/wcharczuk/go-chart/date"
+)
+
+// MarketHoursRange is a special type of range that compresses a time range into just the
+// market (i.e. NYSE operating hours and days) range.
+type MarketHoursRange struct {
+	Min time.Time
+	Max time.Time
+
+	MarketOpen  time.Time
+	MarketClose time.Time
+
+	HolidayProvider date.HolidayProvider
+
+	ValueFormatter ValueFormatter
+
+	Domain int
+}
+
+// IsZero returns if the range is setup or not.
+func (mhr MarketHoursRange) IsZero() bool {
+	return mhr.Min.IsZero() && mhr.Max.IsZero()
+}
+
+// GetMin returns the min value.
+func (mhr MarketHoursRange) GetMin() float64 {
+	return TimeToFloat64(mhr.Min)
+}
+
+// GetMax returns the max value.
+func (mhr MarketHoursRange) GetMax() float64 {
+	return TimeToFloat64(mhr.GetEffectiveMax())
+}
+
+// GetEffectiveMax gets either the close on the max, or the max itself.
+func (mhr MarketHoursRange) GetEffectiveMax() time.Time {
+	maxClose := date.On(mhr.MarketClose, mhr.Max)
+	if maxClose.After(mhr.Max) {
+		return maxClose
+	}
+	return mhr.Max
+}
+
+// SetMin sets the min value.
+func (mhr *MarketHoursRange) SetMin(min float64) {
+	mhr.Min = Float64ToTime(min)
+}
+
+// SetMax sets the max value.
+func (mhr *MarketHoursRange) SetMax(max float64) {
+	mhr.Max = Float64ToTime(max)
+}
+
+// GetDelta gets the delta.
+func (mhr MarketHoursRange) GetDelta() float64 {
+	min := mhr.GetMin()
+	max := mhr.GetMax()
+	return max - min
+}
+
+// GetDomain gets the domain.
+func (mhr MarketHoursRange) GetDomain() int {
+	return mhr.Domain
+}
+
+// SetDomain sets the domain.
+func (mhr *MarketHoursRange) SetDomain(domain int) {
+	mhr.Domain = domain
+}
+
+// GetHolidayProvider coalesces a userprovided holiday provider and the date.DefaultHolidayProvider.
+func (mhr MarketHoursRange) GetHolidayProvider() date.HolidayProvider {
+	if mhr.HolidayProvider == nil {
+		return date.DefaultHolidayProvider
+	}
+	return mhr.HolidayProvider
+}
+
+// GetTicks returns the ticks for the range.
+// This is to override the default continous ticks that would be generated for the range.
+func (mhr *MarketHoursRange) GetTicks(vf ValueFormatter) []Tick {
+	var ticks []Tick
+
+	cursor := date.On(mhr.MarketClose, mhr.Min)
+	maxClose := date.On(mhr.MarketClose, mhr.Max)
+
+	if mhr.Min.Before(cursor) {
+		ticks = append(ticks, Tick{
+			Value: TimeToFloat64(cursor),
+			Label: vf(cursor),
+		})
+	}
+
+	for date.BeforeDate(cursor, maxClose) {
+		if date.IsWeekDay(cursor.Weekday()) && !mhr.GetHolidayProvider()(cursor) {
+			ticks = append(ticks, Tick{
+				Value: TimeToFloat64(cursor),
+				Label: vf(cursor),
+			})
+		}
+
+		cursor = cursor.AddDate(0, 0, 1)
+	}
+
+	endMarketClose := date.On(mhr.MarketClose, cursor)
+	if date.IsWeekDay(endMarketClose.Weekday()) && !mhr.GetHolidayProvider()(endMarketClose) {
+		ticks = append(ticks, Tick{
+			Value: TimeToFloat64(endMarketClose),
+			Label: vf(endMarketClose),
+		})
+	}
+	return ticks
+}
+
+func (mhr MarketHoursRange) String() string {
+	return fmt.Sprintf("MarketHoursRange [%s, %s] => %d", mhr.Min.Format(DefaultDateMinuteFormat), mhr.Max.Format(DefaultDateMinuteFormat), mhr.Domain)
+}
+
+// Translate maps a given value into the ContinuousRange space.
+func (mhr MarketHoursRange) Translate(value float64) int {
+	valueTime := Float64ToTime(value)
+	valueTimeEastern := valueTime.In(date.Eastern())
+	totalSeconds := date.CalculateMarketSecondsBetween(mhr.Min, mhr.GetEffectiveMax(), mhr.MarketOpen, mhr.MarketClose, mhr.HolidayProvider)
+	valueDelta := date.CalculateMarketSecondsBetween(mhr.Min, valueTimeEastern, mhr.MarketOpen, mhr.MarketClose, mhr.HolidayProvider)
+	translated := int((float64(valueDelta) / float64(totalSeconds)) * float64(mhr.Domain))
+	return translated
+}

market_hours_range_test.go

@@ -0,0 +1,61 @@
+package chart
+
+import (
+	"testing"
+	"time"
+
+	assert "github.com/blendlabs/go-assert"
+	"github.com/wcharczuk/go-chart/date"
+)
+
+func TestMarketHoursRangeGetDelta(t *testing.T) {
+	assert := assert.New(t)
+
+	r := &MarketHoursRange{
+		Min:             time.Date(2016, 07, 19, 9, 30, 0, 0, date.Eastern()),
+		Max:             time.Date(2016, 07, 22, 16, 00, 0, 0, date.Eastern()),
+		MarketOpen:      date.NYSEOpen,
+		MarketClose:     date.NYSEClose,
+		HolidayProvider: date.IsNYSEHoliday,
+	}
+
+	assert.NotZero(r.GetDelta())
+}
+
+func TestMarketHoursRangeTranslate(t *testing.T) {
+	assert := assert.New(t)
+
+	r := &MarketHoursRange{
+		Min:             time.Date(2016, 07, 18, 9, 30, 0, 0, date.Eastern()),
+		Max:             time.Date(2016, 07, 22, 16, 00, 0, 0, date.Eastern()),
+		MarketOpen:      date.NYSEOpen,
+		MarketClose:     date.NYSEClose,
+		HolidayProvider: date.IsNYSEHoliday,
+		Domain:          1000,
+	}
+
+	weds := time.Date(2016, 07, 20, 9, 30, 0, 0, date.Eastern())
+
+	assert.Equal(0, r.Translate(TimeToFloat64(r.Min)))
+	assert.Equal(400, r.Translate(TimeToFloat64(weds)))
+	assert.Equal(1000, r.Translate(TimeToFloat64(r.Max)))
+}
+
+func TestMarketHoursRangeGetTicks(t *testing.T) {
+	assert := assert.New(t)
+
+	r := &MarketHoursRange{
+		Min:             time.Date(2016, 07, 18, 9, 30, 0, 0, date.Eastern()),
+		Max:             time.Date(2016, 07, 22, 16, 00, 0, 0, date.Eastern()),
+		MarketOpen:      date.NYSEOpen,
+		MarketClose:     date.NYSEClose,
+		HolidayProvider: date.IsNYSEHoliday,
+		Domain:          1000,
+	}
+
+	ticks := r.GetTicks(TimeValueFormatter)
+	assert.NotEmpty(ticks)
+	assert.Len(ticks, 6)
+	assert.NotEqual(TimeToFloat64(r.Min), ticks[0].Value)
+	assert.NotEmpty(ticks[0].Label)
+}

math.go

@@ -0,0 +1,222 @@
+package chart
+
+import (
+	"math"
+	"time"
+)
+
+const (
+	_pi   = math.Pi
+	_2pi  = 2 * math.Pi
+	_3pi4 = (3 * math.Pi) / 4.0
+	_4pi3 = (4 * math.Pi) / 3.0
+	_3pi2 = (3 * math.Pi) / 2.0
+	_5pi4 = (5 * math.Pi) / 4.0
+	_7pi4 = (7 * math.Pi) / 4.0
+	_pi2  = math.Pi / 2.0
+	_pi4  = math.Pi / 4.0
+	_d2r  = (math.Pi / 180.0)
+	_r2d  = (180.0 / math.Pi)
+)
+
+// TimeToFloat64 returns a float64 representation of a time.
+func TimeToFloat64(t time.Time) float64 {
+	return float64(t.UnixNano())
+}
+
+// Float64ToTime returns a time from a float64.
+func Float64ToTime(tf float64) time.Time {
+	return time.Unix(0, int64(tf))
+}
+
+var (
+	// Math contains helper methods for common math operations.
+	Math = &mathUtil{}
+)
+
+type mathUtil struct{}
+
+// MinAndMax returns both the min and max in one pass.
+func (m mathUtil) MinAndMax(values ...float64) (min float64, max float64) {
+	if len(values) == 0 {
+		return
+	}
+	min = values[0]
+	max = values[0]
+	for _, v := range values {
+		if max < v {
+			max = v
+		}
+		if min > v {
+			min = v
+		}
+	}
+	return
+}
+
+// MinAndMaxOfTime returns the min and max of a given set of times
+// in one pass.
+func (m mathUtil) MinAndMaxOfTime(values ...time.Time) (min time.Time, max time.Time) {
+	if len(values) == 0 {
+		return
+	}
+
+	min = values[0]
+	max = values[0]
+
+	for _, v := range values {
+		if max.Before(v) {
+			max = v
+		}
+		if min.After(v) {
+			min = v
+		}
+	}
+	return
+}
+
+// GetRoundToForDelta returns a `roundTo` value for a given delta.
+func (m mathUtil) GetRoundToForDelta(delta float64) float64 {
+	startingDeltaBound := math.Pow(10.0, 10.0)
+	for cursor := startingDeltaBound; cursor > 0; cursor /= 10.0 {
+		if delta > cursor {
+			return cursor / 10.0
+		}
+	}
+
+	return 0.0
+}
+
+// RoundUp rounds up to a given roundTo value.
+func (m mathUtil) RoundUp(value, roundTo float64) float64 {
+	d1 := math.Ceil(value / roundTo)
+	return d1 * roundTo
+}
+
+// RoundDown rounds down to a given roundTo value.
+func (m mathUtil) RoundDown(value, roundTo float64) float64 {
+	d1 := math.Floor(value / roundTo)
+	return d1 * roundTo
+}
+
+// Normalize returns a set of numbers on the interval [0,1] for a given set of inputs.
+// An example: 4,3,2,1 => 0.4, 0.3, 0.2, 0.1
+// Caveat; the total may be < 1.0; there are going to be issues with irrational numbers etc.
+func (m mathUtil) Normalize(values ...float64) []float64 {
+	var total float64
+	for _, v := range values {
+		total += v
+	}
+	output := make([]float64, len(values))
+	for x, v := range values {
+		output[x] = m.RoundDown(v/total, 0.0001)
+	}
+	return output
+}
+
+// MinInt returns the minimum of a set of integers.
+func (m mathUtil) MinInt(values ...int) int {
+	min := math.MaxInt32
+	for _, v := range values {
+		if v < min {
+			min = v
+		}
+	}
+	return min
+}
+
+// MaxInt returns the maximum of a set of integers.
+func (m mathUtil) MaxInt(values ...int) int {
+	max := math.MinInt32
+	for _, v := range values {
+		if v > max {
+			max = v
+		}
+	}
+	return max
+}
+
+// AbsInt returns the absolute value of an integer.
+func (m mathUtil) AbsInt(value int) int {
+	if value < 0 {
+		return -value
+	}
+	return value
+}
+
+// Sum sums a set of values.
+func (m mathUtil) Sum(values ...float64) float64 {
+	var total float64
+	for _, v := range values {
+		total += v
+	}
+	return total
+}
+
+// SumInt sums a set of values.
+func (m mathUtil) SumInt(values ...int) int {
+	var total int
+	for _, v := range values {
+		total += v
+	}
+	return total
+}
+
+// PercentDifference computes the percentage difference between two values.
+// The formula is (v2-v1)/v1.
+func (m mathUtil) PercentDifference(v1, v2 float64) float64 {
+	if v1 == 0 {
+		return 0
+	}
+	return (v2 - v1) / v1
+}
+
+// DegreesToRadians returns degrees as radians.
+func (m mathUtil) DegreesToRadians(degrees float64) float64 {
+	return degrees * _d2r
+}
+
+// RadiansToDegrees translates a radian value to a degree value.
+func (m mathUtil) RadiansToDegrees(value float64) float64 {
+	return math.Mod(value, _2pi) * _r2d
+}
+
+// PercentToRadians converts a normalized value (0,1) to radians.
+func (m mathUtil) PercentToRadians(pct float64) float64 {
+	return m.DegreesToRadians(360.0 * pct)
+}
+
+// RadianAdd adds a delta to a base in radians.
+func (m mathUtil) RadianAdd(base, delta float64) float64 {
+	value := base + delta
+	if value > _2pi {
+		return math.Mod(value, _2pi)
+	} else if value < 0 {
+		return math.Mod(_2pi+value, _2pi)
+	}
+	return value
+}
+
+// DegreesAdd adds a delta to a base in radians.
+func (m mathUtil) DegreesAdd(baseDegrees, deltaDegrees float64) float64 {
+	value := baseDegrees + deltaDegrees
+	if value > _2pi {
+		return math.Mod(value, 360.0)
+	} else if value < 0 {
+		return math.Mod(360.0+value, 360.0)
+	}
+	return value
+}
+
+// DegreesToCompass returns the degree value in compass / clock orientation.
+func (m mathUtil) DegreesToCompass(deg float64) float64 {
+	return m.DegreesAdd(deg, -90.0)
+}
+
+// CirclePoint returns the absolute position of a circle diameter point given
+// by the radius and the angle.
+func (m mathUtil) CirclePoint(cx, cy int, radius, angleRadians float64) (x, y int) {
+	x = cx + int(radius*math.Sin(angleRadians))
+	y = cy - int(radius*math.Cos(angleRadians))
+	return
+}

math_test.go

@@ -0,0 +1,162 @@
+package chart
+
+import (
+	"testing"
+	"time"
+
+	"github.com/blendlabs/go-assert"
+)
+
+func TestMinAndMax(t *testing.T) {
+	assert := assert.New(t)
+	values := []float64{1.0, 2.0, 3.0, 4.0}
+	min, max := Math.MinAndMax(values...)
+	assert.Equal(1.0, min)
+	assert.Equal(4.0, max)
+}
+
+func TestMinAndMaxReversed(t *testing.T) {
+	assert := assert.New(t)
+	values := []float64{4.0, 2.0, 3.0, 1.0}
+	min, max := Math.MinAndMax(values...)
+	assert.Equal(1.0, min)
+	assert.Equal(4.0, max)
+}
+
+func TestMinAndMaxEmpty(t *testing.T) {
+	assert := assert.New(t)
+	values := []float64{}
+	min, max := Math.MinAndMax(values...)
+	assert.Equal(0.0, min)
+	assert.Equal(0.0, max)
+}
+
+func TestMinAndMaxOfTime(t *testing.T) {
+	assert := assert.New(t)
+	values := []time.Time{
+		time.Now().AddDate(0, 0, -1),
+		time.Now().AddDate(0, 0, -2),
+		time.Now().AddDate(0, 0, -3),
+		time.Now().AddDate(0, 0, -4),
+	}
+	min, max := Math.MinAndMaxOfTime(values...)
+	assert.Equal(values[3], min)
+	assert.Equal(values[0], max)
+}
+
+func TestMinAndMaxOfTimeReversed(t *testing.T) {
+	assert := assert.New(t)
+	values := []time.Time{
+		time.Now().AddDate(0, 0, -4),
+		time.Now().AddDate(0, 0, -2),
+		time.Now().AddDate(0, 0, -3),
+		time.Now().AddDate(0, 0, -1),
+	}
+	min, max := Math.MinAndMaxOfTime(values...)
+	assert.Equal(values[0], min)
+	assert.Equal(values[3], max)
+}
+
+func TestMinAndMaxOfTimeEmpty(t *testing.T) {
+	assert := assert.New(t)
+	values := []time.Time{}
+	min, max := Math.MinAndMaxOfTime(values...)
+	assert.Equal(time.Time{}, min)
+	assert.Equal(time.Time{}, max)
+}
+
+func TestGetRoundToForDelta(t *testing.T) {
+	assert := assert.New(t)
+
+	assert.Equal(100.0, Math.GetRoundToForDelta(1001.00))
+	assert.Equal(10.0, Math.GetRoundToForDelta(101.00))
+	assert.Equal(1.0, Math.GetRoundToForDelta(11.00))
+}
+
+func TestRoundUp(t *testing.T) {
+	assert := assert.New(t)
+	assert.Equal(0.5, Math.RoundUp(0.49, 0.1))
+	assert.Equal(1.0, Math.RoundUp(0.51, 1.0))
+	assert.Equal(0.4999, Math.RoundUp(0.49988, 0.0001))
+}
+
+func TestRoundDown(t *testing.T) {
+	assert := assert.New(t)
+	assert.Equal(0.5, Math.RoundDown(0.51, 0.1))
+	assert.Equal(1.0, Math.RoundDown(1.01, 1.0))
+	assert.Equal(0.5001, Math.RoundDown(0.50011, 0.0001))
+}
+
+func TestPercentDifference(t *testing.T) {
+	assert := assert.New(t)
+
+	assert.Equal(0.5, Math.PercentDifference(1.0, 1.5))
+	assert.Equal(-0.5, Math.PercentDifference(2.0, 1.0))
+}
+
+func TestNormalize(t *testing.T) {
+	assert := assert.New(t)
+
+	values := []float64{10, 9, 8, 7, 6}
+	normalized := Math.Normalize(values...)
+	assert.Len(normalized, 5)
+	assert.Equal(0.25, normalized[0])
+	assert.Equal(0.1499, normalized[4])
+}
+
+var (
+	_degreesToRadians = map[float64]float64{
+		0:   0, // !_2pi b/c no irrational nums in floats.
+		45:  _pi4,
+		90:  _pi2,
+		135: _3pi4,
+		180: _pi,
+		225: _5pi4,
+		270: _3pi2,
+		315: _7pi4,
+	}
+
+	_compassToRadians = map[float64]float64{
+		0:   _pi2,
+		45:  _pi4,
+		90:  0, // !_2pi b/c no irrational nums in floats.
+		135: _7pi4,
+		180: _3pi2,
+		225: _5pi4,
+		270: _pi,
+		315: _3pi4,
+	}
+)
+
+func TestDegreesToRadians(t *testing.T) {
+	assert := assert.New(t)
+
+	for d, r := range _degreesToRadians {
+		assert.Equal(r, Math.DegreesToRadians(d))
+	}
+}
+
+func TestPercentToRadians(t *testing.T) {
+	assert := assert.New(t)
+
+	for d, r := range _degreesToRadians {
+		assert.Equal(r, Math.PercentToRadians(d/360.0))
+	}
+}
+
+func TestRadiansToDegrees(t *testing.T) {
+	assert := assert.New(t)
+
+	for d, r := range _degreesToRadians {
+		assert.Equal(d, Math.RadiansToDegrees(r))
+	}
+}
+
+func TestRadianAdd(t *testing.T) {
+	assert := assert.New(t)
+
+	assert.Equal(_pi, Math.RadianAdd(_pi2, _pi2))
+	assert.Equal(_3pi2, Math.RadianAdd(_pi2, _pi))
+	assert.Equal(_pi, Math.RadianAdd(_pi, _2pi))
+	assert.Equal(_pi, Math.RadianAdd(_pi, -_2pi))
+}

pie_chart.go

@@ -0,0 +1,279 @@
+package chart
+
+import (
+	"errors"
+	"io"
+
+	"github.com/golang/freetype/truetype"
+)
+
+// PieChart is a chart that draws sections of a circle based on percentages.
+type PieChart struct {
+	Title      string
+	TitleStyle Style
+
+	Width  int
+	Height int
+	DPI    float64
+
+	Background Style
+	Canvas     Style
+	SliceStyle Style
+
+	Font        *truetype.Font
+	defaultFont *truetype.Font
+
+	Values   []Value
+	Elements []Renderable
+}
+
+// GetDPI returns the dpi for the chart.
+func (pc PieChart) GetDPI(defaults ...float64) float64 {
+	if pc.DPI == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return DefaultDPI
+	}
+	return pc.DPI
+}
+
+// GetFont returns the text font.
+func (pc PieChart) GetFont() *truetype.Font {
+	if pc.Font == nil {
+		return pc.defaultFont
+	}
+	return pc.Font
+}
+
+// GetWidth returns the chart width or the default value.
+func (pc PieChart) GetWidth() int {
+	if pc.Width == 0 {
+		return DefaultChartWidth
+	}
+	return pc.Width
+}
+
+// GetHeight returns the chart height or the default value.
+func (pc PieChart) GetHeight() int {
+	if pc.Height == 0 {
+		return DefaultChartWidth
+	}
+	return pc.Height
+}
+
+// Render renders the chart with the given renderer to the given io.Writer.
+func (pc PieChart) Render(rp RendererProvider, w io.Writer) error {
+	if len(pc.Values) == 0 {
+		return errors.New("Please provide at least one value.")
+	}
+
+	r, err := rp(pc.GetWidth(), pc.GetHeight())
+	if err != nil {
+		return err
+	}
+
+	if pc.Font == nil {
+		defaultFont, err := GetDefaultFont()
+		if err != nil {
+			return err
+		}
+		pc.defaultFont = defaultFont
+	}
+	r.SetDPI(pc.GetDPI(DefaultDPI))
+
+	canvasBox := pc.getDefaultCanvasBox()
+	canvasBox = pc.getCircleAdjustedCanvasBox(canvasBox)
+
+	pc.drawBackground(r)
+	pc.drawCanvas(r, canvasBox)
+
+	finalValues := pc.finalizeValues(pc.Values)
+	pc.drawSlices(r, canvasBox, finalValues)
+	pc.drawTitle(r)
+	for _, a := range pc.Elements {
+		a(r, canvasBox, pc.styleDefaultsElements())
+	}
+
+	return r.Save(w)
+}
+
+func (pc PieChart) drawBackground(r Renderer) {
+	Draw.Box(r, Box{
+		Right:  pc.GetWidth(),
+		Bottom: pc.GetHeight(),
+	}, pc.getBackgroundStyle())
+}
+
+func (pc PieChart) drawCanvas(r Renderer, canvasBox Box) {
+	Draw.Box(r, canvasBox, pc.getCanvasStyle())
+}
+
+func (pc PieChart) drawTitle(r Renderer) {
+	if len(pc.Title) > 0 && pc.TitleStyle.Show {
+		Draw.TextWithin(r, pc.Title, pc.Box(), pc.styleDefaultsTitle())
+	}
+}
+
+func (pc PieChart) drawSlices(r Renderer, canvasBox Box, values []Value) {
+	cx, cy := canvasBox.Center()
+	diameter := Math.MinInt(canvasBox.Width(), canvasBox.Height())
+	radius := float64(diameter >> 1)
+	labelRadius := (radius * 2.0) / 3.0
+
+	// draw the pie slices
+	var rads, delta, delta2, total float64
+	var lx, ly int
+	for index, v := range values {
+		v.Style.InheritFrom(pc.stylePieChartValue(index)).WriteToRenderer(r)
+
+		r.MoveTo(cx, cy)
+		rads = Math.PercentToRadians(total)
+		delta = Math.PercentToRadians(v.Value)
+
+		r.ArcTo(cx, cy, radius, radius, rads, delta)
+
+		r.LineTo(cx, cy)
+		r.Close()
+		r.FillStroke()
+		total = total + v.Value
+	}
+
+	// draw the labels
+	total = 0
+	for index, v := range values {
+		v.Style.InheritFrom(pc.stylePieChartValue(index)).WriteToRenderer(r)
+		if len(v.Label) > 0 {
+			delta2 = Math.PercentToRadians(total + (v.Value / 2.0))
+			delta2 = Math.RadianAdd(delta2, _pi2)
+			lx, ly = Math.CirclePoint(cx, cy, labelRadius, delta2)
+
+			tb := r.MeasureText(v.Label)
+			lx = lx - (tb.Width() >> 1)
+			ly = ly + (tb.Height() >> 1)
+
+			r.Text(v.Label, lx, ly)
+		}
+		total = total + v.Value
+	}
+}
+
+func (pc PieChart) finalizeValues(values []Value) []Value {
+	return Values(values).Normalize()
+}
+
+func (pc PieChart) getDefaultCanvasBox() Box {
+	return pc.Box()
+}
+
+func (pc PieChart) getCircleAdjustedCanvasBox(canvasBox Box) Box {
+	circleDiameter := Math.MinInt(canvasBox.Width(), canvasBox.Height())
+
+	square := Box{
+		Right:  circleDiameter,
+		Bottom: circleDiameter,
+	}
+
+	return canvasBox.Fit(square)
+}
+
+func (pc PieChart) getBackgroundStyle() Style {
+	return pc.Background.InheritFrom(pc.styleDefaultsBackground())
+}
+
+func (pc PieChart) getCanvasStyle() Style {
+	return pc.Canvas.InheritFrom(pc.styleDefaultsCanvas())
+}
+
+func (pc PieChart) styleDefaultsCanvas() Style {
+	return Style{
+		FillColor:   DefaultCanvasColor,
+		StrokeColor: DefaultCanvasStrokeColor,
+		StrokeWidth: DefaultStrokeWidth,
+	}
+}
+
+func (pc PieChart) styleDefaultsPieChartValue() Style {
+	return Style{
+		StrokeColor: ColorWhite,
+		StrokeWidth: 5.0,
+		FillColor:   ColorWhite,
+	}
+}
+
+func (pc PieChart) stylePieChartValue(index int) Style {
+	return pc.SliceStyle.InheritFrom(Style{
+		StrokeColor: ColorWhite,
+		StrokeWidth: 5.0,
+		FillColor:   GetAlternateColor(index),
+		FontSize:    pc.getScaledFontSize(),
+		FontColor:   ColorWhite,
+		Font:        pc.GetFont(),
+	})
+}
+
+func (pc PieChart) getScaledFontSize() float64 {
+	effectiveDimension := Math.MinInt(pc.GetWidth(), pc.GetHeight())
+	if effectiveDimension >= 2048 {
+		return 48.0
+	} else if effectiveDimension >= 1024 {
+		return 24.0
+	} else if effectiveDimension > 512 {
+		return 18.0
+	} else if effectiveDimension > 256 {
+		return 12.0
+	}
+	return 10.0
+}
+
+func (pc PieChart) styleDefaultsBackground() Style {
+	return Style{
+		FillColor:   DefaultBackgroundColor,
+		StrokeColor: DefaultBackgroundStrokeColor,
+		StrokeWidth: DefaultStrokeWidth,
+	}
+}
+
+func (pc PieChart) styleDefaultsElements() Style {
+	return Style{
+		Font: pc.GetFont(),
+	}
+}
+
+func (pc PieChart) styleDefaultsTitle() Style {
+	return pc.TitleStyle.InheritFrom(Style{
+		FontColor:           ColorWhite,
+		Font:                pc.GetFont(),
+		FontSize:            pc.getTitleFontSize(),
+		TextHorizontalAlign: TextHorizontalAlignCenter,
+		TextVerticalAlign:   TextVerticalAlignTop,
+		TextWrap:            TextWrapWord,
+	})
+}
+
+func (pc PieChart) getTitleFontSize() float64 {
+	effectiveDimension := Math.MinInt(pc.GetWidth(), pc.GetHeight())
+	if effectiveDimension >= 2048 {
+		return 48
+	} else if effectiveDimension >= 1024 {
+		return 24
+	} else if effectiveDimension >= 512 {
+		return 18
+	} else if effectiveDimension >= 256 {
+		return 12
+	}
+	return 10
+}
+
+// Box returns the chart bounds as a box.
+func (pc PieChart) Box() Box {
+	dpr := pc.Background.Padding.GetRight(DefaultBackgroundPadding.Right)
+	dpb := pc.Background.Padding.GetBottom(DefaultBackgroundPadding.Bottom)
+
+	return Box{
+		Top:    pc.Background.Padding.GetTop(DefaultBackgroundPadding.Top),
+		Left:   pc.Background.Padding.GetLeft(DefaultBackgroundPadding.Left),
+		Right:  pc.GetWidth() - dpr,
+		Bottom: pc.GetHeight() - dpb,
+	}
+}

pie_chart_test.go

@@ -0,0 +1,31 @@
+package chart
+
+import (
+	"bytes"
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestPieChart(t *testing.T) {
+	assert := assert.New(t)
+
+	pie := PieChart{
+		Canvas: Style{
+			FillColor: ColorLightGray,
+		},
+		Values: []Value{
+			{Value: 10, Label: "Blue"},
+			{Value: 9, Label: "Green"},
+			{Value: 8, Label: "Gray"},
+			{Value: 7, Label: "Orange"},
+			{Value: 6, Label: "HEANG"},
+			{Value: 5, Label: "??"},
+			{Value: 2, Label: "!!"},
+		},
+	}
+
+	b := bytes.NewBuffer([]byte{})
+	pie.Render(PNG, b)
+	assert.NotZero(b.Len())
+}

range.go

@@ -1,44 +1,41 @@
 package chart
 
-import (
+// NameProvider is a type that returns a name.
-	"fmt"
+type NameProvider interface {
-	"math"
+	GetName() string
-)
-
-// Range represents a boundary for a set of numbers.
-type Range struct {
-	Min    float64
-	Max    float64
-	Domain int
 }
 
-// IsZero returns if the range has been set or not.
+// StyleProvider is a type that returns a style.
-func (r Range) IsZero() bool {
+type StyleProvider interface {
-	return (r.Min == 0 || math.IsNaN(r.Min)) &&
+	GetStyle() Style
-		(r.Max == 0 || math.IsNaN(r.Max)) &&
-		r.Domain == 0
 }
 
-// Delta returns the difference between the min and max value.
+// IsZeroable is a type that returns if it's been set or not.
-func (r Range) Delta() float64 {
+type IsZeroable interface {
-	return r.Max - r.Min
+	IsZero() bool
 }
 
-// String returns a simple string for the range.
+// Stringable is a type that has a string representation.
-func (r Range) String() string {
+type Stringable interface {
-	return fmt.Sprintf("Range [%.2f,%.2f] => %d", r.Min, r.Max, r.Domain)
+	String() string
 }
 
-// Translate maps a given value into the range space.
+// Range is a
-func (r Range) Translate(value float64) int {
+type Range interface {
-	normalized := value - r.Min
+	Stringable
-	ratio := normalized / r.Delta()
+	IsZeroable
-	return int(math.Ceil(ratio * float64(r.Domain)))
-}
 
-// GetRoundedRangeBounds returns some `prettified` range bounds.
+	GetMin() float64
-func (r Range) GetRoundedRangeBounds() (min, max float64) {
+	SetMin(min float64)
-	delta := r.Max - r.Min
+
-	roundTo := GetRoundToForDelta(delta)
+	GetMax() float64
-	return RoundDown(r.Min, roundTo), RoundUp(r.Max, roundTo)
+	SetMax(max float64)
+
+	GetDelta() float64
+
+	GetDomain() int
+	SetDomain(domain int)
+
+	// Translate the range to the domain.
+	Translate(value float64) int
 }

raster_renderer.go

@@ -71,6 +71,16 @@ func (rr *rasterRenderer) LineTo(x, y int) {
 	rr.gc.LineTo(float64(x), float64(y))
 }
 
+// QuadCurveTo implements the interface method.
+func (rr *rasterRenderer) QuadCurveTo(cx, cy, x, y int) {
+	rr.gc.QuadCurveTo(float64(cx), float64(cy), float64(x), float64(y))
+}
+
+// ArcTo implements the interface method.
+func (rr *rasterRenderer) ArcTo(cx, cy int, rx, ry, startAngle, delta float64) {
+	rr.gc.ArcTo(float64(cx), float64(cy), rx, ry, startAngle, delta)
+}
+
 // Close implements the interface method.
 func (rr *rasterRenderer) Close() {
 	rr.gc.Close()

renderer.go

@@ -34,6 +34,14 @@ type Renderer interface {
 	// from the previous point.
 	LineTo(x, y int)
 
+	// QuadCurveTo draws a quad curve.
+	// cx and cy represent the bezier "control points".
+	QuadCurveTo(cx, cy, x, y int)
+
+	// ArcTo draws an arc with a given center (cx,cy)
+	// a given set of radii (rx,ry), a startAngle and delta (in radians).
+	ArcTo(cx, cy int, rx, ry, startAngle, delta float64)
+
 	// Close finalizes a shape as drawn by LineTo.
 	Close()
 

ring_buffer.go

@@ -2,6 +2,7 @@ package chart
 
 import (
 	"fmt"
+	"math"
 	"strings"
 )
 
@@ -200,6 +201,40 @@ func (rb *RingBuffer) String() string {
 	return strings.Join(values, " <= ")
 }
 
+// Average returns the float average of the values in the buffer.
+func (rb *RingBuffer) Average() float64 {
+	var accum float64
+	rb.Each(func(v interface{}) {
+		if typed, isTyped := v.(float64); isTyped {
+			accum += typed
+		}
+	})
+	return accum / float64(rb.Len())
+}
+
+// Variance computes the variance of the buffer.
+func (rb *RingBuffer) Variance() float64 {
+	if rb.Len() == 0 {
+		return 0
+	}
+
+	var variance float64
+	m := rb.Average()
+
+	rb.Each(func(v interface{}) {
+		if n, isTyped := v.(float64); isTyped {
+			variance += (float64(n) - m) * (float64(n) - m)
+		}
+	})
+
+	return variance / float64(rb.Len())
+}
+
+// StdDev returns the standard deviation.
+func (rb *RingBuffer) StdDev() float64 {
+	return math.Pow(rb.Variance(), 0.5)
+}
+
 func arrayClear(source []interface{}, index, length int) {
 	for x := 0; x < length; x++ {
 		absoluteIndex := x + index

sequence.go

@@ -0,0 +1,55 @@
+package chart
+
+import (
+	"math/rand"
+	"time"
+)
+
+var (
+	// Sequence contains some sequence utilities.
+	// These utilities can be useful for generating test data.
+	Sequence = &sequence{}
+)
+
+type sequence struct{}
+
+// Float64 produces an array of floats from [start,end] by optional steps.
+func (s sequence) Float64(start, end float64, steps ...float64) []float64 {
+	var values []float64
+	step := 1.0
+	if len(steps) > 0 {
+		step = steps[0]
+	}
+
+	if start < end {
+		for x := start; x <= end; x += step {
+			values = append(values, x)
+		}
+	} else {
+		for x := start; x >= end; x = x - step {
+			values = append(values, x)
+		}
+	}
+	return values
+}
+
+// Random generates a fixed length sequence of random values between (0, scale).
+func (s sequence) Random(samples int, scale float64) []float64 {
+	rnd := rand.New(rand.NewSource(time.Now().Unix()))
+	values := make([]float64, samples)
+
+	for x := 0; x < samples; x++ {
+		values[x] = rnd.Float64() * scale
+	}
+
+	return values
+}
+
+// Days generates a sequence of timestamps by day, from -days to today.
+func (s sequence) Days(days int) []time.Time {
+	var values []time.Time
+	for day := days; day >= 0; day-- {
+		values = append(values, time.Now().AddDate(0, 0, -day))
+	}
+	return values
+}

sequence_test.go

@@ -0,0 +1,17 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestSequenceFloat64(t *testing.T) {
+	assert := assert.New(t)
+
+	asc := Sequence.Float64(1.0, 10.0)
+	assert.Len(asc, 10)
+
+	desc := Sequence.Float64(10.0, 1.0)
+	assert.Len(desc, 10)
+}

series.go

@@ -3,7 +3,7 @@ package chart
 // Series is an alias to Renderable.
 type Series interface {
 	GetName() string
-	GetYAxis() YAxisType
+	GetYAxis() yAxisType
 	GetStyle() Style
 	Render(r Renderer, canvasBox Box, xrange, yrange Range, s Style)
 }

sma_series.go

@@ -9,7 +9,7 @@ const (
 type SMASeries struct {
 	Name  string
 	Style Style
-	YAxis YAxisType
+	YAxis yAxisType
 
 	Period      int
 	InnerSeries ValueProvider
@@ -26,7 +26,7 @@ func (sma SMASeries) GetStyle() Style {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (sma SMASeries) GetYAxis() YAxisType {
+func (sma SMASeries) GetYAxis() yAxisType {
 	return sma.YAxis
 }
 
@@ -35,6 +35,17 @@ func (sma SMASeries) Len() int {
 	return sma.InnerSeries.Len()
 }
 
+// GetPeriod returns the window size.
+func (sma SMASeries) GetPeriod(defaults ...int) int {
+	if sma.Period == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return DefaultSimpleMovingAveragePeriod
+	}
+	return sma.Period
+}
+
 // GetValue gets a value at a given index.
 func (sma SMASeries) GetValue(index int) (x, y float64) {
 	if sma.InnerSeries == nil {
@@ -59,20 +70,9 @@ func (sma SMASeries) GetLastValue() (x, y float64) {
 	return
 }
 
-// GetPeriod returns the window size.
-func (sma SMASeries) GetPeriod(defaults ...int) int {
-	if sma.Period == 0 {
-		if len(defaults) > 0 {
-			return defaults[0]
-		}
-		return DefaultSimpleMovingAveragePeriod
-	}
-	return sma.Period
-}
-
 func (sma SMASeries) getAverage(index int) float64 {
 	period := sma.GetPeriod()
-	floor := MaxInt(0, index-period)
+	floor := Math.MaxInt(0, index-period)
 	var accum float64
 	var count float64
 	for x := index; x >= floor; x-- {
@@ -85,6 +85,6 @@ func (sma SMASeries) getAverage(index int) float64 {
 
 // Render renders the series.
 func (sma SMASeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	style := sma.Style.WithDefaultsFrom(defaults)
+	style := sma.Style.InheritFrom(defaults)
-	DrawLineSeries(r, canvasBox, xrange, yrange, style, sma)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, sma)
 }

sma_series_test.go

@@ -12,14 +12,14 @@ type mockValueProvider struct {
 }
 
 func (m mockValueProvider) Len() int {
-	return MinInt(len(m.X), len(m.Y))
+	return Math.MinInt(len(m.X), len(m.Y))
 }
 
 func (m mockValueProvider) GetValue(index int) (x, y float64) {
 	if index < 0 {
 		panic("negative index at GetValue()")
 	}
-	if index > MinInt(len(m.X), len(m.Y)) {
+	if index > Math.MinInt(len(m.X), len(m.Y)) {
 		panic("index is outside the length of m.X or m.Y")
 	}
 	x = m.X[index]
@@ -31,8 +31,8 @@ func TestSMASeriesGetValue(t *testing.T) {
 	assert := assert.New(t)
 
 	mockSeries := mockValueProvider{
-		Seq(1.0, 10.0),
+		Sequence.Float64(1.0, 10.0),
-		Seq(10, 1.0),
+		Sequence.Float64(10, 1.0),
 	}
 	assert.Equal(10, mockSeries.Len())
 
@@ -62,8 +62,8 @@ func TestSMASeriesGetLastValueWindowOverlap(t *testing.T) {
 	assert := assert.New(t)
 
 	mockSeries := mockValueProvider{
-		Seq(1.0, 10.0),
+		Sequence.Float64(1.0, 10.0),
-		Seq(10, 1.0),
+		Sequence.Float64(10, 1.0),
 	}
 	assert.Equal(10, mockSeries.Len())
 
@@ -88,8 +88,8 @@ func TestSMASeriesGetLastValue(t *testing.T) {
 	assert := assert.New(t)
 
 	mockSeries := mockValueProvider{
-		Seq(1.0, 100.0),
+		Sequence.Float64(1.0, 100.0),
-		Seq(100, 1.0),
+		Sequence.Float64(100, 1.0),
 	}
 	assert.Equal(100, mockSeries.Len())
 

stacked_bar_chart.go

@@ -0,0 +1,335 @@
+package chart
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"math"
+
+	"github.com/golang/freetype/truetype"
+)
+
+// StackedBar is a bar within a StackedBarChart.
+type StackedBar struct {
+	Name   string
+	Width  int
+	Values []Value
+}
+
+// GetWidth returns the width of the bar.
+func (sb StackedBar) GetWidth() int {
+	if sb.Width == 0 {
+		return 50
+	}
+	return sb.Width
+}
+
+// StackedBarChart is a chart that draws sections of a bar based on percentages.
+type StackedBarChart struct {
+	Title      string
+	TitleStyle Style
+
+	Width  int
+	Height int
+	DPI    float64
+
+	Background Style
+	Canvas     Style
+
+	XAxis Style
+	YAxis Style
+
+	BarSpacing int
+
+	Font        *truetype.Font
+	defaultFont *truetype.Font
+
+	Bars     []StackedBar
+	Elements []Renderable
+}
+
+// GetDPI returns the dpi for the chart.
+func (sbc StackedBarChart) GetDPI(defaults ...float64) float64 {
+	if sbc.DPI == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return DefaultDPI
+	}
+	return sbc.DPI
+}
+
+// GetFont returns the text font.
+func (sbc StackedBarChart) GetFont() *truetype.Font {
+	if sbc.Font == nil {
+		return sbc.defaultFont
+	}
+	return sbc.Font
+}
+
+// GetWidth returns the chart width or the default value.
+func (sbc StackedBarChart) GetWidth() int {
+	if sbc.Width == 0 {
+		return DefaultChartWidth
+	}
+	return sbc.Width
+}
+
+// GetHeight returns the chart height or the default value.
+func (sbc StackedBarChart) GetHeight() int {
+	if sbc.Height == 0 {
+		return DefaultChartWidth
+	}
+	return sbc.Height
+}
+
+// GetBarSpacing returns the spacing between bars.
+func (sbc StackedBarChart) GetBarSpacing() int {
+	if sbc.BarSpacing == 0 {
+		return 100
+	}
+	return sbc.BarSpacing
+}
+
+// Render renders the chart with the given renderer to the given io.Writer.
+func (sbc StackedBarChart) Render(rp RendererProvider, w io.Writer) error {
+	if len(sbc.Bars) == 0 {
+		return errors.New("Please provide at least one bar.")
+	}
+
+	r, err := rp(sbc.GetWidth(), sbc.GetHeight())
+	if err != nil {
+		return err
+	}
+
+	if sbc.Font == nil {
+		defaultFont, err := GetDefaultFont()
+		if err != nil {
+			return err
+		}
+		sbc.defaultFont = defaultFont
+	}
+	r.SetDPI(sbc.GetDPI(DefaultDPI))
+
+	canvasBox := sbc.getAdjustedCanvasBox(r, sbc.getDefaultCanvasBox())
+	sbc.drawBars(r, canvasBox)
+	sbc.drawXAxis(r, canvasBox)
+	sbc.drawYAxis(r, canvasBox)
+
+	sbc.drawTitle(r)
+	for _, a := range sbc.Elements {
+		a(r, canvasBox, sbc.styleDefaultsElements())
+	}
+
+	return r.Save(w)
+}
+
+func (sbc StackedBarChart) drawBars(r Renderer, canvasBox Box) {
+	xoffset := canvasBox.Left
+	for _, bar := range sbc.Bars {
+		sbc.drawBar(r, canvasBox, xoffset, bar)
+		xoffset += (sbc.GetBarSpacing() + bar.GetWidth())
+	}
+}
+
+func (sbc StackedBarChart) drawBar(r Renderer, canvasBox Box, xoffset int, bar StackedBar) int {
+	barSpacing2 := sbc.GetBarSpacing() >> 1
+	bxl := xoffset + barSpacing2
+	bxr := bxl + bar.GetWidth()
+
+	normalizedBarComponents := Values(bar.Values).Normalize()
+	yoffset := canvasBox.Top
+	for index, bv := range normalizedBarComponents {
+		barHeight := int(math.Ceil(bv.Value * float64(canvasBox.Height())))
+		barBox := Box{
+			Top:    yoffset,
+			Left:   bxl,
+			Right:  bxr,
+			Bottom: Math.MinInt(yoffset+barHeight, canvasBox.Bottom-DefaultStrokeWidth),
+		}
+		Draw.Box(r, barBox, bv.Style.InheritFrom(sbc.styleDefaultsStackedBarValue(index)))
+		yoffset += barHeight
+	}
+
+	return bxr
+}
+
+func (sbc StackedBarChart) drawXAxis(r Renderer, canvasBox Box) {
+	if sbc.XAxis.Show {
+		axisStyle := sbc.XAxis.InheritFrom(sbc.styleDefaultsAxes())
+		axisStyle.WriteToRenderer(r)
+
+		r.MoveTo(canvasBox.Left, canvasBox.Bottom)
+		r.LineTo(canvasBox.Right, canvasBox.Bottom)
+		r.Stroke()
+
+		r.MoveTo(canvasBox.Left, canvasBox.Bottom)
+		r.LineTo(canvasBox.Left, canvasBox.Bottom+DefaultVerticalTickHeight)
+		r.Stroke()
+
+		cursor := canvasBox.Left
+		for _, bar := range sbc.Bars {
+
+			barLabelBox := Box{
+				Top:    canvasBox.Bottom + DefaultXAxisMargin,
+				Left:   cursor,
+				Right:  cursor + bar.GetWidth() + sbc.GetBarSpacing(),
+				Bottom: sbc.GetHeight(),
+			}
+			if len(bar.Name) > 0 {
+				Draw.TextWithin(r, bar.Name, barLabelBox, axisStyle)
+			}
+			axisStyle.WriteToRenderer(r)
+			r.MoveTo(barLabelBox.Right, canvasBox.Bottom)
+			r.LineTo(barLabelBox.Right, canvasBox.Bottom+DefaultVerticalTickHeight)
+			r.Stroke()
+			cursor += bar.GetWidth() + sbc.GetBarSpacing()
+		}
+	}
+}
+
+func (sbc StackedBarChart) drawYAxis(r Renderer, canvasBox Box) {
+	if sbc.YAxis.Show {
+		axisStyle := sbc.YAxis.InheritFrom(sbc.styleDefaultsAxes())
+		axisStyle.WriteToRenderer(r)
+		r.MoveTo(canvasBox.Right, canvasBox.Top)
+		r.LineTo(canvasBox.Right, canvasBox.Bottom)
+		r.Stroke()
+
+		r.MoveTo(canvasBox.Right, canvasBox.Bottom)
+		r.LineTo(canvasBox.Right+DefaultHorizontalTickWidth, canvasBox.Bottom)
+		r.Stroke()
+
+		ticks := Sequence.Float64(1.0, 0.0, 0.2)
+		for _, t := range ticks {
+			axisStyle.GetStrokeOptions().WriteToRenderer(r)
+			ty := canvasBox.Bottom - int(t*float64(canvasBox.Height()))
+			r.MoveTo(canvasBox.Right, ty)
+			r.LineTo(canvasBox.Right+DefaultHorizontalTickWidth, ty)
+			r.Stroke()
+
+			axisStyle.GetTextOptions().WriteToRenderer(r)
+			text := fmt.Sprintf("%0.0f%%", t*100)
+
+			tb := r.MeasureText(text)
+			Draw.Text(r, text, canvasBox.Right+DefaultYAxisMargin+5, ty+(tb.Height()>>1), axisStyle)
+		}
+
+	}
+}
+
+func (sbc StackedBarChart) drawTitle(r Renderer) {
+	if len(sbc.Title) > 0 && sbc.TitleStyle.Show {
+		Draw.TextWithin(r, sbc.Title, sbc.Box(), sbc.styleDefaultsTitle())
+	}
+}
+
+func (sbc StackedBarChart) getDefaultCanvasBox() Box {
+	return sbc.Box()
+}
+
+func (sbc StackedBarChart) getAdjustedCanvasBox(r Renderer, canvasBox Box) Box {
+	var totalWidth int
+	for _, bar := range sbc.Bars {
+		totalWidth += bar.GetWidth() + sbc.GetBarSpacing()
+	}
+
+	if sbc.XAxis.Show {
+		xaxisHeight := DefaultVerticalTickHeight
+
+		axisStyle := sbc.XAxis.InheritFrom(sbc.styleDefaultsAxes())
+		axisStyle.WriteToRenderer(r)
+
+		cursor := canvasBox.Left
+		for _, bar := range sbc.Bars {
+			if len(bar.Name) > 0 {
+				barLabelBox := Box{
+					Top:    canvasBox.Bottom + DefaultXAxisMargin,
+					Left:   cursor,
+					Right:  cursor + bar.GetWidth() + sbc.GetBarSpacing(),
+					Bottom: sbc.GetHeight(),
+				}
+				lines := Text.WrapFit(r, bar.Name, barLabelBox.Width(), axisStyle)
+				linesBox := Text.MeasureLines(r, lines, axisStyle)
+
+				xaxisHeight = Math.MaxInt(linesBox.Height()+(2*DefaultXAxisMargin), xaxisHeight)
+			}
+		}
+		return Box{
+			Top:    canvasBox.Top,
+			Left:   canvasBox.Left,
+			Right:  canvasBox.Left + totalWidth,
+			Bottom: sbc.GetHeight() - xaxisHeight,
+		}
+	}
+	return Box{
+		Top:    canvasBox.Top,
+		Left:   canvasBox.Left,
+		Right:  canvasBox.Left + totalWidth,
+		Bottom: canvasBox.Bottom,
+	}
+
+}
+
+// Box returns the chart bounds as a box.
+func (sbc StackedBarChart) Box() Box {
+	dpr := sbc.Background.Padding.GetRight(10)
+	dpb := sbc.Background.Padding.GetBottom(50)
+
+	return Box{
+		Top:    20,
+		Left:   20,
+		Right:  sbc.GetWidth() - dpr,
+		Bottom: sbc.GetHeight() - dpb,
+	}
+}
+
+func (sbc StackedBarChart) styleDefaultsStackedBarValue(index int) Style {
+	return Style{
+		StrokeColor: GetAlternateColor(index),
+		StrokeWidth: 3.0,
+		FillColor:   GetAlternateColor(index),
+	}
+}
+
+func (sbc StackedBarChart) styleDefaultsTitle() Style {
+	return sbc.TitleStyle.InheritFrom(Style{
+		FontColor:           DefaultTextColor,
+		Font:                sbc.GetFont(),
+		FontSize:            sbc.getTitleFontSize(),
+		TextHorizontalAlign: TextHorizontalAlignCenter,
+		TextVerticalAlign:   TextVerticalAlignTop,
+		TextWrap:            TextWrapWord,
+	})
+}
+
+func (sbc StackedBarChart) getTitleFontSize() float64 {
+	effectiveDimension := Math.MinInt(sbc.GetWidth(), sbc.GetHeight())
+	if effectiveDimension >= 2048 {
+		return 48
+	} else if effectiveDimension >= 1024 {
+		return 24
+	} else if effectiveDimension >= 512 {
+		return 18
+	} else if effectiveDimension >= 256 {
+		return 12
+	}
+	return 10
+}
+
+func (sbc StackedBarChart) styleDefaultsAxes() Style {
+	return Style{
+		StrokeColor:         DefaultAxisColor,
+		Font:                sbc.GetFont(),
+		FontSize:            DefaultAxisFontSize,
+		FontColor:           DefaultAxisColor,
+		TextHorizontalAlign: TextHorizontalAlignCenter,
+		TextVerticalAlign:   TextVerticalAlignTop,
+		TextWrap:            TextWrapWord,
+	}
+}
+func (sbc StackedBarChart) styleDefaultsElements() Style {
+	return Style{
+		Font: sbc.GetFont(),
+	}
+}

style.go

@@ -21,6 +21,11 @@ type Style struct {
 	FontSize  float64
 	FontColor drawing.Color
 	Font      *truetype.Font
+
+	TextHorizontalAlign textHorizontalAlign
+	TextVerticalAlign   textVerticalAlign
+	TextWrap            textWrap
+	TextLineSpacing     int
 }
 
 // IsZero returns if the object is set or not.
@@ -28,6 +33,7 @@ func (s Style) IsZero() bool {
 	return s.StrokeColor.IsZero() && s.FillColor.IsZero() && s.StrokeWidth == 0 && s.FontColor.IsZero() && s.FontSize == 0 && s.Font == nil
 }
 
+// String returns a text representation of the style.
 func (s Style) String() string {
 	if s.IsZero() {
 		return "{}"
@@ -78,11 +84,11 @@ func (s Style) String() string {
 	if s.FontSize != 0 {
 		output = append(output, fmt.Sprintf("\"font_size\": \"%0.2fpt\"", s.FontSize))
 	} else {
-		output = append(output, "\"fill_color\": null")
+		output = append(output, "\"font_size\": null")
 	}
 
-	if !s.FillColor.IsZero() {
+	if !s.FontColor.IsZero() {
-		output = append(output, fmt.Sprintf("\"font_color\": %s", s.FillColor.String()))
+		output = append(output, fmt.Sprintf("\"font_color\": %s", s.FontColor.String()))
 	} else {
 		output = append(output, "\"font_color\": null")
 	}
@@ -184,8 +190,78 @@ func (s Style) GetPadding(defaults ...Box) Box {
 	return s.Padding
 }
 
-// WithDefaultsFrom coalesces two styles into a new style.
+// GetTextHorizontalAlign returns the horizontal alignment.
-func (s Style) WithDefaultsFrom(defaults Style) (final Style) {
+func (s Style) GetTextHorizontalAlign(defaults ...textHorizontalAlign) textHorizontalAlign {
+	if s.TextHorizontalAlign == TextHorizontalAlignUnset {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return TextHorizontalAlignUnset
+	}
+	return s.TextHorizontalAlign
+}
+
+// GetTextVerticalAlign returns the vertical alignment.
+func (s Style) GetTextVerticalAlign(defaults ...textVerticalAlign) textVerticalAlign {
+	if s.TextVerticalAlign == TextVerticalAlignUnset {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return TextVerticalAlignUnset
+	}
+	return s.TextVerticalAlign
+}
+
+// GetTextWrap returns the word wrap.
+func (s Style) GetTextWrap(defaults ...textWrap) textWrap {
+	if s.TextWrap == TextWrapUnset {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return TextWrapUnset
+	}
+	return s.TextWrap
+}
+
+// GetTextLineSpacing returns the spacing in pixels between lines of text (vertically).
+func (s Style) GetTextLineSpacing(defaults ...int) int {
+	if s.TextLineSpacing == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return DefaultLineSpacing
+	}
+	return s.TextLineSpacing
+}
+
+// WriteToRenderer passes the style's options to a renderer.
+func (s Style) WriteToRenderer(r Renderer) {
+	r.SetStrokeColor(s.GetStrokeColor())
+	r.SetStrokeWidth(s.GetStrokeWidth())
+	r.SetStrokeDashArray(s.GetStrokeDashArray())
+	r.SetFillColor(s.GetFillColor())
+	r.SetFont(s.GetFont())
+	r.SetFontColor(s.GetFontColor())
+	r.SetFontSize(s.GetFontSize())
+}
+
+// WriteDrawingOptionsToRenderer passes just the drawing style options to a renderer.
+func (s Style) WriteDrawingOptionsToRenderer(r Renderer) {
+	r.SetStrokeColor(s.GetStrokeColor())
+	r.SetStrokeWidth(s.GetStrokeWidth())
+	r.SetStrokeDashArray(s.GetStrokeDashArray())
+	r.SetFillColor(s.GetFillColor())
+}
+
+// WriteTextOptionsToRenderer passes just the text style options to a renderer.
+func (s Style) WriteTextOptionsToRenderer(r Renderer) {
+	r.SetFont(s.GetFont())
+	r.SetFontColor(s.GetFontColor())
+	r.SetFontSize(s.GetFontSize())
+}
+
+// InheritFrom coalesces two styles into a new style.
+func (s Style) InheritFrom(defaults Style) (final Style) {
 	final.StrokeColor = s.GetStrokeColor(defaults.StrokeColor)
 	final.StrokeWidth = s.GetStrokeWidth(defaults.StrokeWidth)
 	final.StrokeDashArray = s.GetStrokeDashArray(defaults.StrokeDashArray)
@@ -194,47 +270,15 @@ func (s Style) WithDefaultsFrom(defaults Style) (final Style) {
 	final.FontSize = s.GetFontSize(defaults.FontSize)
 	final.Font = s.GetFont(defaults.Font)
 	final.Padding = s.GetPadding(defaults.Padding)
+	final.TextHorizontalAlign = s.GetTextHorizontalAlign(defaults.TextHorizontalAlign)
+	final.TextVerticalAlign = s.GetTextVerticalAlign(defaults.TextVerticalAlign)
+	final.TextWrap = s.GetTextWrap(defaults.TextWrap)
+	final.TextLineSpacing = s.GetTextLineSpacing(defaults.TextLineSpacing)
 	return
 }
 
-// SVG returns the style as a svg style string.
+// GetStrokeOptions returns the stroke components.
-func (s Style) SVG(dpi float64) string {
+func (s Style) GetStrokeOptions() Style {
-	sw := s.StrokeWidth
-	sc := s.StrokeColor
-	fc := s.FillColor
-	fs := s.FontSize
-	fnc := s.FontColor
-
-	strokeWidthText := "stroke-width:0"
-	if sw != 0 {
-		strokeWidthText = "stroke-width:" + fmt.Sprintf("%d", int(sw))
-	}
-
-	strokeText := "stroke:none"
-	if !sc.IsZero() {
-		strokeText = "stroke:" + sc.String()
-	}
-
-	fillText := "fill:none"
-	if !fc.IsZero() {
-		fillText = "fill:" + fc.String()
-	}
-
-	fontSizeText := ""
-	if fs != 0 {
-		fontSizeText = "font-size:" + fmt.Sprintf("%.1fpx", drawing.PointsToPixels(dpi, fs))
-	}
-
-	if !fnc.IsZero() {
-		fillText = "fill:" + fnc.String()
-	}
-
-	fontText := s.SVGFontFace()
-	return strings.Join([]string{strokeWidthText, strokeText, fillText, fontSizeText, fontText}, ";")
-}
-
-// SVGStroke returns the stroke components.
-func (s Style) SVGStroke() Style {
 	return Style{
 		StrokeDashArray: s.StrokeDashArray,
 		StrokeColor:     s.StrokeColor,
@@ -242,15 +286,15 @@ func (s Style) SVGStroke() Style {
 	}
 }
 
-// SVGFill returns the fill components.
+// GetFillOptions returns the fill components.
-func (s Style) SVGFill() Style {
+func (s Style) GetFillOptions() Style {
 	return Style{
 		FillColor: s.FillColor,
 	}
 }
 
-// SVGFillAndStroke returns the fill and stroke components.
+// GetFillAndStrokeOptions returns the fill and stroke components.
-func (s Style) SVGFillAndStroke() Style {
+func (s Style) GetFillAndStrokeOptions() Style {
 	return Style{
 		StrokeDashArray: s.StrokeDashArray,
 		FillColor:       s.FillColor,
@@ -259,34 +303,15 @@ func (s Style) SVGFillAndStroke() Style {
 	}
 }
 
-// SVGText returns just the text components of the style.
+// GetTextOptions returns just the text components of the style.
-func (s Style) SVGText() Style {
+func (s Style) GetTextOptions() Style {
 	return Style{
-		FontColor: s.FontColor,
+		FontColor:           s.FontColor,
-		FontSize:  s.FontSize,
+		FontSize:            s.FontSize,
+		Font:                s.Font,
+		TextHorizontalAlign: s.TextHorizontalAlign,
+		TextVerticalAlign:   s.TextVerticalAlign,
+		TextWrap:            s.TextWrap,
+		TextLineSpacing:     s.TextLineSpacing,
 	}
 }
-
-// SVGFontFace returns the font face for the style.
-func (s Style) SVGFontFace() string {
-	family := "sans-serif"
-	if s.GetFont() != nil {
-		name := s.GetFont().Name(truetype.NameIDFontFamily)
-		if len(name) != 0 {
-			family = fmt.Sprintf(`'%s',%s`, name, family)
-		}
-	}
-	return fmt.Sprintf("font-family:%s", family)
-}
-
-// SVGStrokeDashArray returns the stroke-dasharray property of a style.
-func (s Style) SVGStrokeDashArray() string {
-	if len(s.StrokeDashArray) > 0 {
-		var values []string
-		for _, v := range s.StrokeDashArray {
-			values = append(values, fmt.Sprintf("%0.1f", v))
-		}
-		return "stroke-dasharray=\"" + strings.Join(values, ", ") + "\""
-	}
-	return ""
-}

style_test.go

@@ -1,7 +1,6 @@
 package chart
 
 import (
-	"strings"
 	"testing"
 
 	"github.com/blendlabs/go-assert"
@@ -142,33 +141,11 @@ func TestStyleWithDefaultsFrom(t *testing.T) {
 		Padding:     DefaultBackgroundPadding,
 	}
 
-	coalesced := unset.WithDefaultsFrom(set)
+	coalesced := unset.InheritFrom(set)
 	assert.Equal(set, coalesced)
 }
 
-func TestStyleSVG(t *testing.T) {
+func TestStyleGetStrokeOptions(t *testing.T) {
-	assert := assert.New(t)
-
-	f, err := GetDefaultFont()
-	assert.Nil(err)
-
-	set := Style{
-		StrokeColor: drawing.ColorWhite,
-		StrokeWidth: 5.0,
-		FillColor:   drawing.ColorWhite,
-		FontColor:   drawing.ColorWhite,
-		Font:        f,
-		Padding:     DefaultBackgroundPadding,
-	}
-
-	svgString := set.SVG(DefaultDPI)
-	assert.NotEmpty(svgString)
-	assert.True(strings.Contains(svgString, "stroke:rgba(255,255,255,1.0)"))
-	assert.True(strings.Contains(svgString, "stroke-width:5"))
-	assert.True(strings.Contains(svgString, "fill:rgba(255,255,255,1.0)"))
-}
-
-func TestStyleSVGStroke(t *testing.T) {
 	assert := assert.New(t)
 
 	set := Style{
@@ -178,14 +155,14 @@ func TestStyleSVGStroke(t *testing.T) {
 		FontColor:   drawing.ColorWhite,
 		Padding:     DefaultBackgroundPadding,
 	}
-	svgStroke := set.SVGStroke()
+	svgStroke := set.GetStrokeOptions()
 	assert.False(svgStroke.StrokeColor.IsZero())
 	assert.NotZero(svgStroke.StrokeWidth)
 	assert.True(svgStroke.FillColor.IsZero())
 	assert.True(svgStroke.FontColor.IsZero())
 }
 
-func TestStyleSVGFill(t *testing.T) {
+func TestStyleGetFillOptions(t *testing.T) {
 	assert := assert.New(t)
 
 	set := Style{
@@ -195,14 +172,14 @@ func TestStyleSVGFill(t *testing.T) {
 		FontColor:   drawing.ColorWhite,
 		Padding:     DefaultBackgroundPadding,
 	}
-	svgFill := set.SVGFill()
+	svgFill := set.GetFillOptions()
 	assert.False(svgFill.FillColor.IsZero())
 	assert.Zero(svgFill.StrokeWidth)
 	assert.True(svgFill.StrokeColor.IsZero())
 	assert.True(svgFill.FontColor.IsZero())
 }
 
-func TestStyleSVGFillAndStroke(t *testing.T) {
+func TestStyleGetFillAndStrokeOptions(t *testing.T) {
 	assert := assert.New(t)
 
 	set := Style{
@@ -212,14 +189,14 @@ func TestStyleSVGFillAndStroke(t *testing.T) {
 		FontColor:   drawing.ColorWhite,
 		Padding:     DefaultBackgroundPadding,
 	}
-	svgFillAndStroke := set.SVGFillAndStroke()
+	svgFillAndStroke := set.GetFillAndStrokeOptions()
 	assert.False(svgFillAndStroke.FillColor.IsZero())
 	assert.NotZero(svgFillAndStroke.StrokeWidth)
 	assert.False(svgFillAndStroke.StrokeColor.IsZero())
 	assert.True(svgFillAndStroke.FontColor.IsZero())
 }
 
-func TestStyleSVGText(t *testing.T) {
+func TestStyleGetTextOptions(t *testing.T) {
 	assert := assert.New(t)
 
 	set := Style{
@@ -229,7 +206,7 @@ func TestStyleSVGText(t *testing.T) {
 		FontColor:   drawing.ColorWhite,
 		Padding:     DefaultBackgroundPadding,
 	}
-	svgStroke := set.SVGText()
+	svgStroke := set.GetTextOptions()
 	assert.True(svgStroke.StrokeColor.IsZero())
 	assert.Zero(svgStroke.StrokeWidth)
 	assert.True(svgStroke.FillColor.IsZero())

text.go

@@ -0,0 +1,164 @@
+package chart
+
+import "strings"
+
+// TextHorizontalAlign is an enum for the horizontal alignment options.
+type textHorizontalAlign int
+
+const (
+	// TextHorizontalAlignUnset is the unset state for text horizontal alignment.
+	TextHorizontalAlignUnset textHorizontalAlign = 0
+	// TextHorizontalAlignLeft aligns a string horizontally so that it's left ligature starts at horizontal pixel 0.
+	TextHorizontalAlignLeft textHorizontalAlign = 1
+	// TextHorizontalAlignCenter left aligns a string horizontally so that there are equal pixels
+	// to the left and to the right of a string within a box.
+	TextHorizontalAlignCenter textHorizontalAlign = 2
+	// TextHorizontalAlignRight right aligns a string horizontally so that the right ligature ends at the right-most pixel
+	// of a box.
+	TextHorizontalAlignRight textHorizontalAlign = 3
+)
+
+// TextWrap is an enum for the word wrap options.
+type textWrap int
+
+const (
+	// TextWrapUnset is the unset state for text wrap options.
+	TextWrapUnset textWrap = 0
+	// TextWrapNone will spill text past horizontal boundaries.
+	TextWrapNone textWrap = 1
+	// TextWrapWord will split a string on words (i.e. spaces) to fit within a horizontal boundary.
+	TextWrapWord textWrap = 2
+	// TextWrapRune will split a string on a rune (i.e. utf-8 codepage) to fit within a horizontal boundary.
+	TextWrapRune textWrap = 3
+)
+
+// TextVerticalAlign is an enum for the vertical alignment options.
+type textVerticalAlign int
+
+const (
+	// TextVerticalAlignUnset is the unset state for vertical alignment options.
+	TextVerticalAlignUnset textVerticalAlign = 0
+	// TextVerticalAlignBaseline aligns text according to the "baseline" of the string, or where a normal ascender begins.
+	TextVerticalAlignBaseline textVerticalAlign = 1
+	// TextVerticalAlignBottom aligns the text according to the lowers pixel of any of the ligatures (ex. g or q both extend below the baseline).
+	TextVerticalAlignBottom textVerticalAlign = 2
+	// TextVerticalAlignMiddle aligns the text so that there is an equal amount of space above and below the top and bottom of the ligatures.
+	TextVerticalAlignMiddle textVerticalAlign = 3
+	// TextVerticalAlignMiddleBaseline aligns the text veritcally so that there is an equal number of pixels above and below the baseline of the string.
+	TextVerticalAlignMiddleBaseline textVerticalAlign = 4
+	// TextVerticalAlignTop alignts the text so that the top of the ligatures are at y-pixel 0 in the container.
+	TextVerticalAlignTop textVerticalAlign = 5
+)
+
+var (
+	// Text contains utilities for text.
+	Text = &text{}
+)
+
+// TextStyle encapsulates text style options.
+type TextStyle struct {
+	HorizontalAlign textHorizontalAlign
+	VerticalAlign   textVerticalAlign
+	Wrap            textWrap
+}
+
+type text struct{}
+
+func (t text) WrapFit(r Renderer, value string, width int, style Style) []string {
+	switch style.TextWrap {
+	case TextWrapRune:
+		return t.WrapFitRune(r, value, width, style)
+	case TextWrapWord:
+		return t.WrapFitWord(r, value, width, style)
+	}
+	return []string{value}
+}
+
+func (t text) WrapFitWord(r Renderer, value string, width int, style Style) []string {
+	style.WriteToRenderer(r)
+
+	var output []string
+	var line string
+	var word string
+
+	var textBox Box
+
+	for _, c := range value {
+		if c == rune('\n') { // commit the line to output
+			output = append(output, t.Trim(line+word))
+			line = ""
+			word = ""
+			continue
+		}
+
+		textBox = r.MeasureText(line + word + string(c))
+
+		if textBox.Width() >= width {
+			output = append(output, t.Trim(line))
+			line = word
+			word = string(c)
+			continue
+		}
+
+		if c == rune(' ') || c == rune('\t') {
+			line = line + word + string(c)
+			word = ""
+			continue
+		}
+		word = word + string(c)
+	}
+
+	return append(output, t.Trim(line+word))
+}
+
+func (t text) WrapFitRune(r Renderer, value string, width int, style Style) []string {
+	style.WriteToRenderer(r)
+
+	var output []string
+	var line string
+	var textBox Box
+	for _, c := range value {
+		if c == rune('\n') {
+			output = append(output, line)
+			line = ""
+			continue
+		}
+
+		textBox = r.MeasureText(line + string(c))
+
+		if textBox.Width() >= width {
+			output = append(output, line)
+			line = string(c)
+			continue
+		}
+		line = line + string(c)
+	}
+	return t.appendLast(output, line)
+}
+
+func (t text) Trim(value string) string {
+	return strings.Trim(value, " \t\n\r")
+}
+
+func (t text) MeasureLines(r Renderer, lines []string, style Style) Box {
+	style.WriteTextOptionsToRenderer(r)
+	var output Box
+	for index, line := range lines {
+		lineBox := r.MeasureText(line)
+		output.Right = Math.MaxInt(lineBox.Right, output.Right)
+		output.Bottom += lineBox.Height()
+		if index < len(lines)-1 {
+			output.Bottom += +style.GetTextLineSpacing()
+		}
+	}
+	return output
+}
+
+func (t text) appendLast(lines []string, text string) []string {
+	if len(lines) == 0 {
+		return []string{text}
+	}
+	lastLine := lines[len(lines)-1]
+	lines[len(lines)-1] = lastLine + text
+	return lines
+}

text_test.go

@@ -0,0 +1,60 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestTextWrapWord(t *testing.T) {
+	assert := assert.New(t)
+
+	r, err := PNG(1024, 1024)
+	assert.Nil(err)
+	f, err := GetDefaultFont()
+	assert.Nil(err)
+
+	basicTextStyle := Style{Font: f, FontSize: 24}
+
+	output := Text.WrapFitWord(r, "this is a test string", 100, basicTextStyle)
+	assert.NotEmpty(output)
+	assert.Len(output, 3)
+
+	for _, line := range output {
+		basicTextStyle.WriteToRenderer(r)
+		lineBox := r.MeasureText(line)
+		assert.True(lineBox.Width() < 100, line+": "+lineBox.String())
+	}
+	assert.Equal("this is", output[0])
+	assert.Equal("a test", output[1])
+	assert.Equal("string", output[2])
+
+	output = Text.WrapFitWord(r, "foo", 100, basicTextStyle)
+	assert.Len(output, 1)
+	assert.Equal("foo", output[0])
+
+	// test that it handles newlines.
+	output = Text.WrapFitWord(r, "this\nis\na\ntest\nstring", 100, basicTextStyle)
+	assert.Len(output, 5)
+
+	// test that it handles newlines and long lines.
+	output = Text.WrapFitWord(r, "this\nis\na\ntest\nstring that is very long", 100, basicTextStyle)
+	assert.Len(output, 8)
+}
+
+func TestTextWrapRune(t *testing.T) {
+	assert := assert.New(t)
+
+	r, err := PNG(1024, 1024)
+	assert.Nil(err)
+	f, err := GetDefaultFont()
+	assert.Nil(err)
+
+	basicTextStyle := Style{Font: f, FontSize: 24}
+
+	output := Text.WrapFitRune(r, "this is a test string", 150, basicTextStyle)
+	assert.NotEmpty(output)
+	assert.Len(output, 2)
+	assert.Equal("this is a t", output[0])
+	assert.Equal("est string", output[1])
+}

tick.go

@@ -1,21 +1,10 @@
 package chart
 
-// GenerateTicksWithStep generates a set of ticks.
+import "math"
-func GenerateTicksWithStep(ra Range, step float64, vf ValueFormatter) []Tick {
-	var ticks []Tick
-	min, max := ra.Min, ra.Max
-	for cursor := min; cursor <= max; cursor += step {
-		ticks = append(ticks, Tick{
-			Value: cursor,
-			Label: vf(cursor),
-		})
 
-		// this guard is in place in case step is super, super small.
+// TicksProvider is a type that provides ticks.
-		if len(ticks) > DefaultTickCountSanityCheck {
+type TicksProvider interface {
-			return ticks
+	GetTicks(vf ValueFormatter) []Tick
-		}
-	}
-	return ticks
 }
 
 // Tick represents a label on an axis.
@@ -41,3 +30,52 @@ func (t Ticks) Swap(i, j int) {
 func (t Ticks) Less(i, j int) bool {
 	return t[i].Value < t[j].Value
 }
+
+// GenerateContinuousTicksWithStep generates a set of ticks.
+func GenerateContinuousTicksWithStep(ra Range, step float64, vf ValueFormatter, includeMax bool) []Tick {
+	var ticks []Tick
+	min, max := ra.GetMin(), ra.GetMax()
+	for cursor := min; cursor <= max; cursor += step {
+		ticks = append(ticks, Tick{
+			Value: cursor,
+			Label: vf(cursor),
+		})
+
+		// this guard is in place in case step is super, super small.
+		if len(ticks) > DefaultTickCountSanityCheck {
+			return ticks
+		}
+	}
+	if includeMax {
+		ticks = append(ticks, Tick{
+			Value: ra.GetMax(),
+			Label: vf(ra.GetMax()),
+		})
+	}
+	return ticks
+}
+
+// CalculateContinuousTickStep calculates the continous range interval between ticks.
+func CalculateContinuousTickStep(r Renderer, ra Range, isVertical bool, style Style, vf ValueFormatter) float64 {
+	r.SetFont(style.GetFont())
+	r.SetFontSize(style.GetFontSize())
+	if isVertical {
+		label := vf(ra.GetMin())
+		tb := r.MeasureText(label)
+		count := int(math.Ceil(float64(ra.GetDomain()) / float64(tb.Height()+DefaultMinimumTickVerticalSpacing)))
+		return ra.GetDelta() / float64(count)
+	}
+
+	// take a cut at determining the 'widest' value.
+	l0 := vf(ra.GetMin())
+	ln := vf(ra.GetMax())
+	ll := l0
+	if len(ln) > len(l0) {
+		ll = ln
+	}
+	llb := r.MeasureText(ll)
+	textWidth := llb.Width()
+	width := textWidth + DefaultMinimumTickHorizontalSpacing
+	count := int(math.Ceil(float64(ra.GetDomain()) / float64(width)))
+	return ra.GetDelta() / float64(count)
+}

tick_test.go

@@ -9,6 +9,6 @@ import (
 func TestGenerateTicksWithStep(t *testing.T) {
 	assert := assert.New(t)
 
-	ticks := GenerateTicksWithStep(Range{Min: 1.0, Max: 10.0, Domain: 100}, 1.0, FloatValueFormatter)
+	ticks := GenerateContinuousTicksWithStep(&ContinuousRange{Min: 1.0, Max: 10.0, Domain: 100}, 1.0, FloatValueFormatter, false)
 	assert.Len(ticks, 10)
 }

time_series.go

@@ -7,7 +7,7 @@ type TimeSeries struct {
 	Name  string
 	Style Style
 
-	YAxis YAxisType
+	YAxis yAxisType
 
 	XValues []time.Time
 	YValues []float64
@@ -50,12 +50,12 @@ func (ts TimeSeries) GetValueFormatters() (x, y ValueFormatter) {
 }
 
 // GetYAxis returns which YAxis the series draws on.
-func (ts TimeSeries) GetYAxis() YAxisType {
+func (ts TimeSeries) GetYAxis() yAxisType {
 	return ts.YAxis
 }
 
 // Render renders the series.
 func (ts TimeSeries) Render(r Renderer, canvasBox Box, xrange, yrange Range, defaults Style) {
-	style := ts.Style.WithDefaultsFrom(defaults)
+	style := ts.Style.InheritFrom(defaults)
-	DrawLineSeries(r, canvasBox, xrange, yrange, style, ts)
+	Draw.LineSeries(r, canvasBox, xrange, yrange, style, ts)
 }

util.go

@@ -1,172 +0,0 @@
-package chart
-
-import (
-	"fmt"
-	"math"
-	"math/rand"
-	"time"
-)
-
-// Float is an alias for float64 that provides a better .String() method.
-type Float float64
-
-// String returns the string representation of a float.
-func (f Float) String() string {
-	return fmt.Sprintf("%.2f", f)
-}
-
-// TimeToFloat64 returns a float64 representation of a time.
-func TimeToFloat64(t time.Time) float64 {
-	return float64(t.UnixNano())
-}
-
-// MinAndMax returns both the min and max in one pass.
-func MinAndMax(values ...float64) (min float64, max float64) {
-	if len(values) == 0 {
-		return
-	}
-	min = values[0]
-	max = values[0]
-	for _, v := range values {
-		if max < v {
-			max = v
-		}
-		if min > v {
-			min = v
-		}
-	}
-	return
-}
-
-// MinAndMaxOfTime returns the min and max of a given set of times
-// in one pass.
-func MinAndMaxOfTime(values ...time.Time) (min time.Time, max time.Time) {
-	if len(values) == 0 {
-		return
-	}
-
-	min = values[0]
-	max = values[0]
-
-	for _, v := range values {
-		if max.Before(v) {
-			max = v
-		}
-		if min.After(v) {
-			min = v
-		}
-	}
-	return
-}
-
-// Slices generates N slices that span the total.
-// The resulting array will be intermediate indexes until total.
-func Slices(count int, total float64) []float64 {
-	var values []float64
-	sliceWidth := float64(total) / float64(count)
-	for cursor := 0.0; cursor < total; cursor += sliceWidth {
-		values = append(values, cursor)
-	}
-	return values
-}
-
-// GetRoundToForDelta returns a `roundTo` value for a given delta.
-func GetRoundToForDelta(delta float64) float64 {
-	startingDeltaBound := math.Pow(10.0, 10.0)
-	for cursor := startingDeltaBound; cursor > 0; cursor /= 10.0 {
-		if delta > cursor {
-			return cursor / 10.0
-		}
-	}
-
-	return 0.0
-}
-
-// RoundUp rounds up to a given roundTo value.
-func RoundUp(value, roundTo float64) float64 {
-	d1 := math.Ceil(value / roundTo)
-	return d1 * roundTo
-}
-
-// RoundDown rounds down to a given roundTo value.
-func RoundDown(value, roundTo float64) float64 {
-	d1 := math.Floor(value / roundTo)
-	return d1 * roundTo
-}
-
-// MinInt returns the minimum of a set of integers.
-func MinInt(values ...int) int {
-	min := math.MaxInt32
-	for _, v := range values {
-		if v < min {
-			min = v
-		}
-	}
-	return min
-}
-
-// MaxInt returns the maximum of a set of integers.
-func MaxInt(values ...int) int {
-	max := math.MinInt32
-	for _, v := range values {
-		if v > max {
-			max = v
-		}
-	}
-	return max
-}
-
-// AbsInt returns the absolute value of an integer.
-func AbsInt(value int) int {
-	if value < 0 {
-		return -value
-	}
-	return value
-}
-
-// Seq produces an array of floats from [start,end] by optional steps.
-func Seq(start, end float64, steps ...float64) []float64 {
-	var values []float64
-	step := 1.0
-	if len(steps) > 0 {
-		step = steps[0]
-	}
-
-	if start < end {
-		for x := start; x <= end; x += step {
-			values = append(values, x)
-		}
-	} else {
-		for x := start; x >= end; x = x - step {
-			values = append(values, x)
-		}
-	}
-	return values
-}
-
-// SeqRand generates a random sequence.
-func SeqRand(samples int, scale float64) []float64 {
-	rnd := rand.New(rand.NewSource(time.Now().Unix()))
-	values := make([]float64, samples)
-
-	for x := 0; x < samples; x++ {
-		values[x] = rnd.Float64() * scale
-	}
-
-	return values
-}
-
-// SeqDays generates a sequence of timestamps by day, from -days to today.
-func SeqDays(days int) []time.Time {
-	var values []time.Time
-	for day := days; day >= 0; day-- {
-		values = append(values, time.Now().AddDate(0, 0, -day))
-	}
-	return values
-}
-
-// PercentDifference computes the percentage difference between two values.
-// The formula is (v2-v1)/v1.
-func PercentDifference(v1, v2 float64) float64 {
-	return (v2 - v1) / v1
-}

util_test.go

@@ -1,102 +0,0 @@
-package chart
-
-import (
-	"testing"
-	"time"
-
-	"github.com/blendlabs/go-assert"
-)
-
-func TestMinAndMax(t *testing.T) {
-	assert := assert.New(t)
-	values := []float64{1.0, 2.0, 3.0, 4.0}
-	min, max := MinAndMax(values...)
-	assert.Equal(1.0, min)
-	assert.Equal(4.0, max)
-}
-
-func TestMinAndMaxReversed(t *testing.T) {
-	assert := assert.New(t)
-	values := []float64{4.0, 2.0, 3.0, 1.0}
-	min, max := MinAndMax(values...)
-	assert.Equal(1.0, min)
-	assert.Equal(4.0, max)
-}
-
-func TestMinAndMaxEmpty(t *testing.T) {
-	assert := assert.New(t)
-	values := []float64{}
-	min, max := MinAndMax(values...)
-	assert.Equal(0.0, min)
-	assert.Equal(0.0, max)
-}
-
-func TestMinAndMaxOfTime(t *testing.T) {
-	assert := assert.New(t)
-	values := []time.Time{
-		time.Now().AddDate(0, 0, -1),
-		time.Now().AddDate(0, 0, -2),
-		time.Now().AddDate(0, 0, -3),
-		time.Now().AddDate(0, 0, -4),
-	}
-	min, max := MinAndMaxOfTime(values...)
-	assert.Equal(values[3], min)
-	assert.Equal(values[0], max)
-}
-
-func TestMinAndMaxOfTimeReversed(t *testing.T) {
-	assert := assert.New(t)
-	values := []time.Time{
-		time.Now().AddDate(0, 0, -4),
-		time.Now().AddDate(0, 0, -2),
-		time.Now().AddDate(0, 0, -3),
-		time.Now().AddDate(0, 0, -1),
-	}
-	min, max := MinAndMaxOfTime(values...)
-	assert.Equal(values[0], min)
-	assert.Equal(values[3], max)
-}
-
-func TestMinAndMaxOfTimeEmpty(t *testing.T) {
-	assert := assert.New(t)
-	values := []time.Time{}
-	min, max := MinAndMaxOfTime(values...)
-	assert.Equal(time.Time{}, min)
-	assert.Equal(time.Time{}, max)
-}
-
-func TestSlices(t *testing.T) {
-	assert := assert.New(t)
-
-	s := Slices(10, 100)
-	assert.Len(s, 10)
-	assert.Equal(0, s[0])
-	assert.Equal(10, s[1])
-	assert.Equal(20, s[2])
-	assert.Equal(90, s[9])
-}
-
-func TestGetRoundToForDelta(t *testing.T) {
-	assert := assert.New(t)
-
-	assert.Equal(100.0, GetRoundToForDelta(1001.00))
-	assert.Equal(10.0, GetRoundToForDelta(101.00))
-	assert.Equal(1.0, GetRoundToForDelta(11.00))
-}
-
-func TestSeq(t *testing.T) {
-	assert := assert.New(t)
-
-	asc := Seq(1.0, 10.0)
-	assert.Len(asc, 10)
-
-	desc := Seq(10.0, 1.0)
-	assert.Len(desc, 10)
-}
-
-func TestPercentDifference(t *testing.T) {
-	assert := assert.New(t)
-
-	assert.Equal(0.5, PercentDifference(1.0, 1.5))
-	assert.Equal(-0.5, PercentDifference(2.0, 1.0))
-}

value.go

@@ -0,0 +1,46 @@
+package chart
+
+// Value is a chart value.
+type Value struct {
+	Style Style
+	Label string
+	Value float64
+}
+
+// Values is an array of Value.
+type Values []Value
+
+// Values returns the values.
+func (vs Values) Values() []float64 {
+	values := make([]float64, len(vs))
+	for index, v := range vs {
+		values[index] = v.Value
+	}
+	return values
+}
+
+// ValuesNormalized returns normalized values.
+func (vs Values) ValuesNormalized() []float64 {
+	return Math.Normalize(vs.Values()...)
+}
+
+// Normalize returns the values normalized.
+func (vs Values) Normalize() []Value {
+	output := make([]Value, len(vs))
+	total := Math.Sum(vs.Values()...)
+	for index, v := range vs {
+		output[index] = Value{
+			Style: v.Style,
+			Label: v.Label,
+			Value: Math.RoundDown(v.Value/total, 0.0001),
+		}
+	}
+	return output
+}
+
+// Value2 is a two axis value.
+type Value2 struct {
+	Style          Style
+	Label          string
+	XValue, YValue float64
+}

value_test.go

@@ -0,0 +1,69 @@
+package chart
+
+import (
+	"testing"
+
+	assert "github.com/blendlabs/go-assert"
+)
+
+func TestValuesValues(t *testing.T) {
+	assert := assert.New(t)
+
+	vs := []Value{
+		{Value: 10, Label: "Blue"},
+		{Value: 9, Label: "Green"},
+		{Value: 8, Label: "Gray"},
+		{Value: 7, Label: "Orange"},
+		{Value: 6, Label: "HEANG"},
+		{Value: 5, Label: "??"},
+		{Value: 2, Label: "!!"},
+	}
+
+	values := Values(vs).Values()
+	assert.Len(values, 7)
+	assert.Equal(10, values[0])
+	assert.Equal(9, values[1])
+	assert.Equal(8, values[2])
+	assert.Equal(7, values[3])
+	assert.Equal(6, values[4])
+	assert.Equal(5, values[5])
+	assert.Equal(2, values[6])
+}
+
+func TestValuesValuesNormalized(t *testing.T) {
+	assert := assert.New(t)
+
+	vs := []Value{
+		{Value: 10, Label: "Blue"},
+		{Value: 9, Label: "Green"},
+		{Value: 8, Label: "Gray"},
+		{Value: 7, Label: "Orange"},
+		{Value: 6, Label: "HEANG"},
+		{Value: 5, Label: "??"},
+		{Value: 2, Label: "!!"},
+	}
+
+	values := Values(vs).ValuesNormalized()
+	assert.Len(values, 7)
+	assert.Equal(0.2127, values[0])
+	assert.Equal(0.0425, values[6])
+}
+
+func TestValuesNormalize(t *testing.T) {
+	assert := assert.New(t)
+
+	vs := []Value{
+		{Value: 10, Label: "Blue"},
+		{Value: 9, Label: "Green"},
+		{Value: 8, Label: "Gray"},
+		{Value: 7, Label: "Orange"},
+		{Value: 6, Label: "HEANG"},
+		{Value: 5, Label: "??"},
+		{Value: 2, Label: "!!"},
+	}
+
+	values := Values(vs).Normalize()
+	assert.Len(values, 7)
+	assert.Equal(0.2127, values[0].Value)
+	assert.Equal(0.0425, values[6].Value)
+}

vector_renderer.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"math"
 	"strings"
 
 	"golang.org/x/image/font"
@@ -76,6 +77,32 @@ func (vr *vectorRenderer) LineTo(x, y int) {
 	vr.p = append(vr.p, fmt.Sprintf("L %d %d", x, y))
 }
 
+// QuadCurveTo draws a quad curve.
+func (vr *vectorRenderer) QuadCurveTo(cx, cy, x, y int) {
+	vr.p = append(vr.p, fmt.Sprintf("Q%d,%d %d,%d", cx, cy, x, y))
+}
+
+func (vr *vectorRenderer) ArcTo(cx, cy int, rx, ry, startAngle, delta float64) {
+	startAngle = Math.RadianAdd(startAngle, _pi2)
+	endAngle := Math.RadianAdd(startAngle, delta)
+
+	startx := cx + int(rx*math.Sin(startAngle))
+	starty := cy - int(ry*math.Cos(startAngle))
+
+	if len(vr.p) > 0 {
+		vr.p = append(vr.p, fmt.Sprintf("L %d %d", startx, starty))
+	} else {
+		vr.p = append(vr.p, fmt.Sprintf("M %d %d", startx, starty))
+	}
+
+	endx := cx + int(rx*math.Sin(endAngle))
+	endy := cy - int(ry*math.Cos(endAngle))
+
+	dd := Math.RadiansToDegrees(delta)
+
+	vr.p = append(vr.p, fmt.Sprintf("A %d %d %0.2f 0 1 %d %d", int(rx), int(ry), dd, endx, endy))
+}
+
 // Close closes a shape.
 func (vr *vectorRenderer) Close() {
 	vr.p = append(vr.p, fmt.Sprintf("Z"))
@@ -83,30 +110,28 @@ func (vr *vectorRenderer) Close() {
 
 // Stroke draws the path with no fill.
 func (vr *vectorRenderer) Stroke() {
-	vr.drawPath(vr.s.SVGStroke())
+	vr.drawPath(vr.s.GetStrokeOptions())
 }
 
 // Fill draws the path with no stroke.
 func (vr *vectorRenderer) Fill() {
-	vr.drawPath(vr.s.SVGFill())
+	vr.drawPath(vr.s.GetFillOptions())
 }
 
 // FillStroke draws the path with both fill and stroke.
 func (vr *vectorRenderer) FillStroke() {
-	s := vr.s.SVGFillAndStroke()
+	vr.drawPath(vr.s.GetFillAndStrokeOptions())
-	vr.drawPath(s)
 }
 
 // drawPath draws a path.
 func (vr *vectorRenderer) drawPath(s Style) {
-	vr.c.Path(strings.Join(vr.p, "\n"), &s)
+	vr.c.Path(strings.Join(vr.p, "\n"), vr.s.GetFillAndStrokeOptions())
 	vr.p = []string{} // clear the path
 }
 
 // Circle implements the interface method.
 func (vr *vectorRenderer) Circle(radius float64, x, y int) {
-	style := vr.s.SVGFillAndStroke()
+	vr.c.Circle(x, y, int(radius), vr.s.GetFillAndStrokeOptions())
-	vr.c.Circle(x, y, int(radius), &style)
 }
 
 // SetFont implements the interface method.
@@ -126,8 +151,7 @@ func (vr *vectorRenderer) SetFontSize(size float64) {
 
 // Text draws a text blob.
 func (vr *vectorRenderer) Text(body string, x, y int) {
-	style := vr.s.SVGText()
+	vr.c.Text(x, y, body, vr.s.GetTextOptions())
-	vr.c.Text(x, y, body, &style)
 }
 
 // MeasureText uses the truetype font drawer to measure the width of text.
@@ -173,22 +197,82 @@ func (c *canvas) Start(width, height int) {
 	c.w.Write([]byte(fmt.Sprintf(`<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="%d" height="%d">\n`, c.width, c.height)))
 }
 
-func (c *canvas) Path(d string, style *Style) {
+func (c *canvas) Path(d string, style Style) {
 	var strokeDashArrayProperty string
 	if len(style.StrokeDashArray) > 0 {
-		strokeDashArrayProperty = style.SVGStrokeDashArray()
+		strokeDashArrayProperty = c.getStrokeDashArray(style)
 	}
-	c.w.Write([]byte(fmt.Sprintf(`<path %s d="%s" style="%s"/>\n`, strokeDashArrayProperty, d, style.SVG(c.dpi))))
+	c.w.Write([]byte(fmt.Sprintf(`<path %s d="%s" style="%s"/>\n`, strokeDashArrayProperty, d, c.styleAsSVG(style))))
 }
 
-func (c *canvas) Text(x, y int, body string, style *Style) {
+func (c *canvas) Text(x, y int, body string, style Style) {
-	c.w.Write([]byte(fmt.Sprintf(`<text x="%d" y="%d" style="%s">%s</text>`, x, y, style.SVG(c.dpi), body)))
+	c.w.Write([]byte(fmt.Sprintf(`<text x="%d" y="%d" style="%s">%s</text>`, x, y, c.styleAsSVG(style), body)))
 }
 
-func (c *canvas) Circle(x, y, r int, style *Style) {
+func (c *canvas) Circle(x, y, r int, style Style) {
-	c.w.Write([]byte(fmt.Sprintf(`<circle cx="%d" cy="%d" r="%d" style="%s">`, x, y, r, style.SVG(c.dpi))))
+	c.w.Write([]byte(fmt.Sprintf(`<circle cx="%d" cy="%d" r="%d" style="%s">`, x, y, r, c.styleAsSVG(style))))
 }
 
 func (c *canvas) End() {
 	c.w.Write([]byte("</svg>"))
 }
+
+// getStrokeDashArray returns the stroke-dasharray property of a style.
+func (c *canvas) getStrokeDashArray(s Style) string {
+	if len(s.StrokeDashArray) > 0 {
+		var values []string
+		for _, v := range s.StrokeDashArray {
+			values = append(values, fmt.Sprintf("%0.1f", v))
+		}
+		return "stroke-dasharray=\"" + strings.Join(values, ", ") + "\""
+	}
+	return ""
+}
+
+// GetFontFace returns the font face for the style.
+func (c *canvas) getFontFace(s Style) string {
+	family := "sans-serif"
+	if s.GetFont() != nil {
+		name := s.GetFont().Name(truetype.NameIDFontFamily)
+		if len(name) != 0 {
+			family = fmt.Sprintf(`'%s',%s`, name, family)
+		}
+	}
+	return fmt.Sprintf("font-family:%s", family)
+}
+
+// styleAsSVG returns the style as a svg style string.
+func (c *canvas) styleAsSVG(s Style) string {
+	sw := s.StrokeWidth
+	sc := s.StrokeColor
+	fc := s.FillColor
+	fs := s.FontSize
+	fnc := s.FontColor
+
+	strokeWidthText := "stroke-width:0"
+	if sw != 0 {
+		strokeWidthText = "stroke-width:" + fmt.Sprintf("%d", int(sw))
+	}
+
+	strokeText := "stroke:none"
+	if !sc.IsZero() {
+		strokeText = "stroke:" + sc.String()
+	}
+
+	fillText := "fill:none"
+	if !fc.IsZero() {
+		fillText = "fill:" + fc.String()
+	}
+
+	fontSizeText := ""
+	if fs != 0 {
+		fontSizeText = "font-size:" + fmt.Sprintf("%.1fpx", drawing.PointsToPixels(c.dpi, fs))
+	}
+
+	if !fnc.IsZero() {
+		fillText = "fill:" + fnc.String()
+	}
+
+	fontText := c.getFontFace(s)
+	return strings.Join([]string{strokeWidthText, strokeText, fillText, fontSizeText, fontText}, ";")
+}

vector_renderer_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/blendlabs/go-assert"
+	"github.com/wcharczuk/go-chart/drawing"
 )
 
 func TestVectorRendererPath(t *testing.T) {
@@ -50,3 +51,27 @@ func TestVectorRendererMeasureText(t *testing.T) {
 	assert.Equal(21, tb.Width())
 	assert.Equal(15, tb.Height())
 }
+
+func TestCanvasStyleSVG(t *testing.T) {
+	assert := assert.New(t)
+
+	f, err := GetDefaultFont()
+	assert.Nil(err)
+
+	set := Style{
+		StrokeColor: drawing.ColorWhite,
+		StrokeWidth: 5.0,
+		FillColor:   drawing.ColorWhite,
+		FontColor:   drawing.ColorWhite,
+		Font:        f,
+		Padding:     DefaultBackgroundPadding,
+	}
+
+	canvas := &canvas{dpi: DefaultDPI}
+
+	svgString := canvas.styleAsSVG(set)
+	assert.NotEmpty(svgString)
+	assert.True(strings.Contains(svgString, "stroke:rgba(255,255,255,1.0)"))
+	assert.True(strings.Contains(svgString, "stroke-width:5"))
+	assert.True(strings.Contains(svgString, "fill:rgba(255,255,255,1.0)"))
+}

xaxis.go

@@ -13,6 +13,8 @@ type XAxis struct {
 	Range          Range
 	Ticks          []Tick
 
+	TickPosition tickPosition
+
 	GridLines      []GridLine
 	GridMajorStyle Style
 	GridMinorStyle Style
@@ -28,42 +30,31 @@ func (xa XAxis) GetStyle() Style {
 	return xa.Style
 }
 
-// GetTicks returns the ticks for a series. It coalesces between user provided ticks and
+// GetTickPosition returns the tick position option for the axis.
-// generated ticks.
+func (xa XAxis) GetTickPosition(defaults ...tickPosition) tickPosition {
+	if xa.TickPosition == TickPositionUnset {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+		return TickPositionUnderTick
+	}
+	return xa.TickPosition
+}
+
+// GetTicks returns the ticks for a series.
+// The coalesce priority is:
+// 	- User Supplied Ticks (i.e. Ticks array on the axis itself).
+// 	- Range ticks (i.e. if the range provides ticks).
+//	- Generating continuous ticks based on minimum spacing and canvas width.
 func (xa XAxis) GetTicks(r Renderer, ra Range, defaults Style, vf ValueFormatter) []Tick {
 	if len(xa.Ticks) > 0 {
 		return xa.Ticks
 	}
-	return xa.generateTicks(r, ra, defaults, vf)
+	if tp, isTickProvider := ra.(TicksProvider); isTickProvider {
-}
+		return tp.GetTicks(vf)
-
-func (xa XAxis) generateTicks(r Renderer, ra Range, defaults Style, vf ValueFormatter) []Tick {
-	step := xa.getTickStep(r, ra, defaults, vf)
-	return GenerateTicksWithStep(ra, step, vf)
-}
-
-func (xa XAxis) getTickStep(r Renderer, ra Range, defaults Style, vf ValueFormatter) float64 {
-	tickCount := xa.getTickCount(r, ra, defaults, vf)
-	step := ra.Delta() / float64(tickCount)
-	return step
-}
-
-func (xa XAxis) getTickCount(r Renderer, ra Range, defaults Style, vf ValueFormatter) int {
-	r.SetFont(xa.Style.GetFont(defaults.GetFont()))
-	r.SetFontSize(xa.Style.GetFontSize(defaults.GetFontSize(DefaultFontSize)))
-
-	// take a cut at determining the 'widest' value.
-	l0 := vf(ra.Min)
-	ln := vf(ra.Max)
-	ll := l0
-	if len(ln) > len(l0) {
-		ll = ln
 	}
-	llb := r.MeasureText(ll)
+	step := CalculateContinuousTickStep(r, ra, false, xa.Style.InheritFrom(defaults), vf)
-	textWidth := llb.Width()
+	return GenerateContinuousTicksWithStep(ra, step, vf, xa.TickPosition == TickPositionBetweenTicks)
-	width := textWidth + DefaultMinimumTickHorizontalSpacing
-	count := int(math.Ceil(float64(ra.Domain) / float64(width)))
-	return count
 }
 
 // GetGridLines returns the gridlines for the axis.
@@ -71,18 +62,12 @@ func (xa XAxis) GetGridLines(ticks []Tick) []GridLine {
 	if len(xa.GridLines) > 0 {
 		return xa.GridLines
 	}
-	return GenerateGridLines(ticks, true)
+	return GenerateGridLines(ticks, xa.GridMajorStyle, xa.GridMinorStyle, true)
 }
 
 // Measure returns the bounds of the axis.
 func (xa XAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, ticks []Tick) Box {
-	r.SetStrokeColor(xa.Style.GetStrokeColor(defaults.StrokeColor))
+	xa.Style.InheritFrom(defaults).WriteToRenderer(r)
-	r.SetStrokeWidth(xa.Style.GetStrokeWidth(defaults.StrokeWidth))
-	r.SetStrokeDashArray(xa.Style.GetStrokeDashArray())
-	r.SetFont(xa.Style.GetFont(defaults.GetFont()))
-	r.SetFontColor(xa.Style.GetFontColor(DefaultAxisColor))
-	r.SetFontSize(xa.Style.GetFontSize(defaults.GetFontSize()))
-
 	sort.Sort(Ticks(ticks))
 
 	var left, right, top, bottom = math.MaxInt32, 0, math.MaxInt32, 0
@@ -94,10 +79,10 @@ func (xa XAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 		tx := canvasBox.Left + lx
 		ty := canvasBox.Bottom + DefaultXAxisMargin + tb.Height()
 
-		top = MinInt(top, canvasBox.Bottom)
+		top = Math.MinInt(top, canvasBox.Bottom)
-		left = MinInt(left, tx-(tb.Width()>>1))
+		left = Math.MinInt(left, tx-(tb.Width()>>1))
-		right = MaxInt(right, tx+(tb.Width()>>1))
+		right = Math.MaxInt(right, tx+(tb.Width()>>1))
-		bottom = MaxInt(bottom, ty)
+		bottom = Math.MaxInt(bottom, ty)
 	}
 
 	return Box{
@@ -110,37 +95,58 @@ func (xa XAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 
 // Render renders the axis
 func (xa XAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, ticks []Tick) {
-	r.SetStrokeColor(xa.Style.GetStrokeColor(defaults.StrokeColor))
+	tickStyle := xa.Style.InheritFrom(defaults)
-	r.SetStrokeWidth(xa.Style.GetStrokeWidth(defaults.StrokeWidth))
-	r.SetStrokeDashArray(xa.Style.GetStrokeDashArray())
-	r.SetFont(xa.Style.GetFont(defaults.GetFont()))
-	r.SetFontColor(xa.Style.GetFontColor(DefaultAxisColor))
-	r.SetFontSize(xa.Style.GetFontSize(defaults.GetFontSize()))
 
+	tickStyle.GetStrokeOptions().WriteToRenderer(r)
 	r.MoveTo(canvasBox.Left, canvasBox.Bottom)
 	r.LineTo(canvasBox.Right, canvasBox.Bottom)
 	r.Stroke()
 
 	sort.Sort(Ticks(ticks))
 
-	for _, t := range ticks {
+	tp := xa.GetTickPosition()
+
+	var tx, ty int
+	for index, t := range ticks {
 		v := t.Value
 		lx := ra.Translate(v)
 		tb := r.MeasureText(t.Label)
-		tx := canvasBox.Left + lx
-		ty := canvasBox.Bottom + DefaultXAxisMargin + tb.Height()
-		r.Text(t.Label, tx-tb.Width()>>1, ty)
 
+		tx = canvasBox.Left + lx
+		ty = canvasBox.Bottom + DefaultXAxisMargin + tb.Height()
+
+		tickStyle.GetStrokeOptions().WriteToRenderer(r)
 		r.MoveTo(tx, canvasBox.Bottom)
 		r.LineTo(tx, canvasBox.Bottom+DefaultVerticalTickHeight)
 		r.Stroke()
+
+		switch tp {
+		case TickPositionUnderTick:
+			tickStyle.GetTextOptions().WriteToRenderer(r)
+			r.Text(t.Label, tx-tb.Width()>>1, ty)
+		case TickPositionBetweenTicks:
+			if index > 0 {
+				llx := ra.Translate(ticks[index-1].Value)
+				ltx := canvasBox.Left + llx
+				Draw.TextWithin(r, t.Label, Box{
+					Left:   ltx,
+					Right:  tx,
+					Top:    canvasBox.Bottom + DefaultXAxisMargin,
+					Bottom: canvasBox.Bottom + DefaultXAxisMargin + tb.Height(),
+				}, tickStyle.InheritFrom(Style{TextHorizontalAlign: TextHorizontalAlignCenter}))
+			}
+		}
+
 	}
 
 	if xa.GridMajorStyle.Show || xa.GridMinorStyle.Show {
 		for _, gl := range xa.GetGridLines(ticks) {
-			if (gl.IsMinor && xa.GridMinorStyle.Show) ||
+			if (gl.IsMinor && xa.GridMinorStyle.Show) || (!gl.IsMinor && xa.GridMajorStyle.Show) {
-				(!gl.IsMinor && xa.GridMajorStyle.Show) {
+				defaults := xa.GridMajorStyle
-				gl.Render(r, canvasBox, ra)
+				if gl.IsMinor {
+					defaults = xa.GridMinorStyle
+				}
+				gl.Render(r, canvasBox, ra, defaults)
 			}
 		}
 	}

xaxis_test.go

@@ -6,46 +6,6 @@ import (
 	"github.com/blendlabs/go-assert"
 )
 
-func TestXAxisGetTickCount(t *testing.T) {
-	assert := assert.New(t)
-
-	r, err := PNG(1024, 1024)
-	assert.Nil(err)
-
-	f, err := GetDefaultFont()
-	assert.Nil(err)
-
-	xa := XAxis{}
-	xr := Range{Min: 10, Max: 100, Domain: 1024}
-	styleDefaults := Style{
-		Font:     f,
-		FontSize: 10.0,
-	}
-	vf := FloatValueFormatter
-	count := xa.getTickCount(r, xr, styleDefaults, vf)
-	assert.Equal(16, count)
-}
-
-func TestXAxisGetTickStep(t *testing.T) {
-	assert := assert.New(t)
-
-	r, err := PNG(1024, 1024)
-	assert.Nil(err)
-
-	f, err := GetDefaultFont()
-	assert.Nil(err)
-
-	xa := XAxis{}
-	xr := Range{Min: 10, Max: 100, Domain: 1024}
-	styleDefaults := Style{
-		Font:     f,
-		FontSize: 10.0,
-	}
-	vf := FloatValueFormatter
-	step := xa.getTickStep(r, xr, styleDefaults, vf)
-	assert.Equal(xr.Delta()/16.0, step)
-}
-
 func TestXAxisGetTicks(t *testing.T) {
 	assert := assert.New(t)
 
@@ -56,7 +16,7 @@ func TestXAxisGetTicks(t *testing.T) {
 	assert.Nil(err)
 
 	xa := XAxis{}
-	xr := Range{Min: 10, Max: 100, Domain: 1024}
+	xr := &ContinuousRange{Min: 10, Max: 100, Domain: 1024}
 	styleDefaults := Style{
 		Font:     f,
 		FontSize: 10.0,
@@ -78,7 +38,7 @@ func TestXAxisGetTicksWithUserDefaults(t *testing.T) {
 	xa := XAxis{
 		Ticks: []Tick{{Value: 1.0, Label: "1.0"}},
 	}
-	xr := Range{Min: 10, Max: 100, Domain: 1024}
+	xr := &ContinuousRange{Min: 10, Max: 100, Domain: 1024}
 	styleDefaults := Style{
 		Font:     f,
 		FontSize: 10.0,
@@ -87,3 +47,21 @@ func TestXAxisGetTicksWithUserDefaults(t *testing.T) {
 	ticks := xa.GetTicks(r, xr, styleDefaults, vf)
 	assert.Len(ticks, 1)
 }
+
+func TestXAxisMeasure(t *testing.T) {
+	assert := assert.New(t)
+
+	f, err := GetDefaultFont()
+	assert.Nil(err)
+	style := Style{
+		Font:     f,
+		FontSize: 10.0,
+	}
+	r, err := PNG(100, 100)
+	assert.Nil(err)
+	ticks := []Tick{{Value: 1.0, Label: "1.0"}, {Value: 2.0, Label: "2.0"}, {Value: 3.0, Label: "3.0"}}
+	xa := XAxis{}
+	xab := xa.Measure(r, Box{0, 0, 100, 100}, &ContinuousRange{Min: 1.0, Max: 3.0, Domain: 100}, style, ticks)
+	assert.Equal(122, xab.Width())
+	assert.Equal(21, xab.Height())
+}

yaxis.go

@@ -13,13 +13,14 @@ type YAxis struct {
 
 	Zero GridLine
 
-	AxisType YAxisType
+	AxisType yAxisType
 
 	ValueFormatter ValueFormatter
 	Range          Range
-	Ticks          []Tick
 
-	GridLines      []GridLine
+	Ticks     []Tick
+	GridLines []GridLine
+
 	GridMajorStyle Style
 	GridMinorStyle Style
 }
@@ -34,35 +35,20 @@ func (ya YAxis) GetStyle() Style {
 	return ya.Style
 }
 
-// GetTicks returns the ticks for a series. It coalesces between user provided ticks and
+// GetTicks returns the ticks for a series.
-// generated ticks.
+// The coalesce priority is:
+// 	- User Supplied Ticks (i.e. Ticks array on the axis itself).
+// 	- Range ticks (i.e. if the range provides ticks).
+//	- Generating continuous ticks based on minimum spacing and canvas width.
 func (ya YAxis) GetTicks(r Renderer, ra Range, defaults Style, vf ValueFormatter) []Tick {
 	if len(ya.Ticks) > 0 {
 		return ya.Ticks
 	}
-	return ya.generateTicks(r, ra, defaults, vf)
+	if tp, isTickProvider := ra.(TicksProvider); isTickProvider {
-}
+		return tp.GetTicks(vf)
-
+	}
-func (ya YAxis) generateTicks(r Renderer, ra Range, defaults Style, vf ValueFormatter) []Tick {
+	step := CalculateContinuousTickStep(r, ra, true, ya.Style.InheritFrom(defaults), vf)
-	step := ya.getTickStep(r, ra, defaults, vf)
+	return GenerateContinuousTicksWithStep(ra, step, vf, true)
-	ticks := GenerateTicksWithStep(ra, step, vf)
-	return ticks
-}
-
-func (ya YAxis) getTickStep(r Renderer, ra Range, defaults Style, vf ValueFormatter) float64 {
-	tickCount := ya.getTickCount(r, ra, defaults, vf)
-	step := ra.Delta() / float64(tickCount)
-	return step
-}
-
-func (ya YAxis) getTickCount(r Renderer, ra Range, defaults Style, vf ValueFormatter) int {
-	r.SetFont(ya.Style.GetFont(defaults.GetFont()))
-	r.SetFontSize(ya.Style.GetFontSize(defaults.GetFontSize(DefaultFontSize)))
-	//given the domain, figure out how many ticks we can draw ...
-	label := vf(ra.Min)
-	tb := r.MeasureText(label)
-	count := int(math.Ceil(float64(ra.Domain) / float64(tb.Height()+DefaultMinimumTickVerticalSpacing)))
-	return count
 }
 
 // GetGridLines returns the gridlines for the axis.
@@ -70,16 +56,12 @@ func (ya YAxis) GetGridLines(ticks []Tick) []GridLine {
 	if len(ya.GridLines) > 0 {
 		return ya.GridLines
 	}
-	return GenerateGridLines(ticks, false)
+	return GenerateGridLines(ticks, ya.GridMajorStyle, ya.GridMinorStyle, false)
 }
 
 // Measure returns the bounds of the axis.
 func (ya YAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, ticks []Tick) Box {
-	r.SetStrokeColor(ya.Style.GetStrokeColor(defaults.StrokeColor))
+	ya.Style.InheritFrom(defaults).WriteToRenderer(r)
-	r.SetStrokeWidth(ya.Style.GetStrokeWidth(defaults.StrokeWidth))
-	r.SetFont(ya.Style.GetFont(defaults.GetFont()))
-	r.SetFontColor(ya.Style.GetFontColor(DefaultAxisColor))
-	r.SetFontSize(ya.Style.GetFontSize(defaults.GetFontSize()))
 
 	sort.Sort(Ticks(ticks))
 
@@ -103,13 +85,13 @@ func (ya YAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 
 		if ya.AxisType == YAxisPrimary {
 			minx = canvasBox.Right
-			maxx = MaxInt(maxx, tx+tb.Width())
+			maxx = Math.MaxInt(maxx, tx+tb.Width())
 		} else if ya.AxisType == YAxisSecondary {
-			minx = MinInt(minx, finalTextX)
+			minx = Math.MinInt(minx, finalTextX)
-			maxx = MaxInt(maxx, tx)
+			maxx = Math.MaxInt(maxx, tx)
 		}
-		miny = MinInt(miny, ly-tb.Height()>>1)
+		miny = Math.MinInt(miny, ly-tb.Height()>>1)
-		maxy = MaxInt(maxy, ly+tb.Height()>>1)
+		maxy = Math.MaxInt(maxy, ly+tb.Height()>>1)
 	}
 
 	return Box{
@@ -122,11 +104,7 @@ func (ya YAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 
 // Render renders the axis.
 func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, ticks []Tick) {
-	r.SetStrokeColor(ya.Style.GetStrokeColor(defaults.StrokeColor))
+	ya.Style.InheritFrom(defaults).WriteToRenderer(r)
-	r.SetStrokeWidth(ya.Style.GetStrokeWidth(defaults.StrokeWidth))
-	r.SetFont(ya.Style.GetFont(defaults.GetFont()))
-	r.SetFontColor(ya.Style.GetFontColor(DefaultAxisColor))
-	r.SetFontSize(ya.Style.GetFontSize(defaults.GetFontSize(DefaultFontSize)))
 
 	sort.Sort(Ticks(ticks))
 
@@ -170,14 +148,17 @@ func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 	}
 
 	if ya.Zero.Style.Show {
-		ya.Zero.Render(r, canvasBox, ra)
+		ya.Zero.Render(r, canvasBox, ra, Style{})
 	}
 
 	if ya.GridMajorStyle.Show || ya.GridMinorStyle.Show {
 		for _, gl := range ya.GetGridLines(ticks) {
-			if (gl.IsMinor && ya.GridMinorStyle.Show) ||
+			if (gl.IsMinor && ya.GridMinorStyle.Show) || (!gl.IsMinor && ya.GridMajorStyle.Show) {
-				(!gl.IsMinor && ya.GridMajorStyle.Show) {
+				defaults := ya.GridMajorStyle
-				gl.Render(r, canvasBox, ra)
+				if gl.IsMinor {
+					defaults = ya.GridMinorStyle
+				}
+				gl.Render(r, canvasBox, ra, defaults)
 			}
 		}
 	}

yaxis_test.go

@@ -6,46 +6,6 @@ import (
 	"github.com/blendlabs/go-assert"
 )
 
-func TestYAxisGetTickCount(t *testing.T) {
-	assert := assert.New(t)
-
-	r, err := PNG(1024, 1024)
-	assert.Nil(err)
-
-	f, err := GetDefaultFont()
-	assert.Nil(err)
-
-	ya := YAxis{}
-	yr := Range{Min: 10, Max: 100, Domain: 1024}
-	styleDefaults := Style{
-		Font:     f,
-		FontSize: 10.0,
-	}
-	vf := FloatValueFormatter
-	count := ya.getTickCount(r, yr, styleDefaults, vf)
-	assert.Equal(34, count)
-}
-
-func TestYAxisGetTickStep(t *testing.T) {
-	assert := assert.New(t)
-
-	r, err := PNG(1024, 1024)
-	assert.Nil(err)
-
-	f, err := GetDefaultFont()
-	assert.Nil(err)
-
-	ya := YAxis{}
-	yr := Range{Min: 10, Max: 100, Domain: 1024}
-	styleDefaults := Style{
-		Font:     f,
-		FontSize: 10.0,
-	}
-	vf := FloatValueFormatter
-	step := ya.getTickStep(r, yr, styleDefaults, vf)
-	assert.Equal(yr.Delta()/34.0, step)
-}
-
 func TestYAxisGetTicks(t *testing.T) {
 	assert := assert.New(t)
 
@@ -56,14 +16,14 @@ func TestYAxisGetTicks(t *testing.T) {
 	assert.Nil(err)
 
 	ya := YAxis{}
-	yr := Range{Min: 10, Max: 100, Domain: 1024}
+	yr := &ContinuousRange{Min: 10, Max: 100, Domain: 1024}
 	styleDefaults := Style{
 		Font:     f,
 		FontSize: 10.0,
 	}
 	vf := FloatValueFormatter
 	ticks := ya.GetTicks(r, yr, styleDefaults, vf)
-	assert.Len(ticks, 35)
+	assert.Len(ticks, 36)
 }
 
 func TestYAxisGetTicksWithUserDefaults(t *testing.T) {
@@ -78,7 +38,7 @@ func TestYAxisGetTicksWithUserDefaults(t *testing.T) {
 	ya := YAxis{
 		Ticks: []Tick{{Value: 1.0, Label: "1.0"}},
 	}
-	yr := Range{Min: 10, Max: 100, Domain: 1024}
+	yr := &ContinuousRange{Min: 10, Max: 100, Domain: 1024}
 	styleDefaults := Style{
 		Font:     f,
 		FontSize: 10.0,
@@ -87,3 +47,39 @@ func TestYAxisGetTicksWithUserDefaults(t *testing.T) {
 	ticks := ya.GetTicks(r, yr, styleDefaults, vf)
 	assert.Len(ticks, 1)
 }
+
+func TestYAxisMeasure(t *testing.T) {
+	assert := assert.New(t)
+
+	f, err := GetDefaultFont()
+	assert.Nil(err)
+	style := Style{
+		Font:     f,
+		FontSize: 10.0,
+	}
+	r, err := PNG(100, 100)
+	assert.Nil(err)
+	ticks := []Tick{{Value: 1.0, Label: "1.0"}, {Value: 2.0, Label: "2.0"}, {Value: 3.0, Label: "3.0"}}
+	ya := YAxis{}
+	yab := ya.Measure(r, Box{0, 0, 100, 100}, &ContinuousRange{Min: 1.0, Max: 3.0, Domain: 100}, style, ticks)
+	assert.Equal(32, yab.Width())
+	assert.Equal(110, yab.Height())
+}
+
+func TestYAxisSecondaryMeasure(t *testing.T) {
+	assert := assert.New(t)
+
+	f, err := GetDefaultFont()
+	assert.Nil(err)
+	style := Style{
+		Font:     f,
+		FontSize: 10.0,
+	}
+	r, err := PNG(100, 100)
+	assert.Nil(err)
+	ticks := []Tick{{Value: 1.0, Label: "1.0"}, {Value: 2.0, Label: "2.0"}, {Value: 3.0, Label: "3.0"}}
+	ya := YAxis{AxisType: YAxisSecondary}
+	yab := ya.Measure(r, Box{0, 0, 100, 100}, &ContinuousRange{Min: 1.0, Max: 3.0, Domain: 100}, style, ticks)
+	assert.Equal(32, yab.Width())
+	assert.Equal(110, yab.Height())
+}