Merge pull request #13 from wcharczuk/text-rotation

Adds `TextRotationDegrees`

.vscode/launch.json

@@ -0,0 +1,18 @@
+{
+	"version": "0.2.0",
+	"configurations": [
+		{
+			"name": "Launch",
+			"type": "go",
+			"request": "launch",
+			"mode": "test",
+			"remotePath": "",
+			"port": 2345,
+			"host": "127.0.0.1",
+			"program": "${workspaceRoot}",
+			"env": {},
+			"args": [],
+			"showLog": true
+		}
+	]
+}

_examples/request_timings/main.go

@@ -2,23 +2,33 @@ package main
 
 import (
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
-	util "github.com/blendlabs/go-util"
 	"github.com/wcharczuk/go-chart"
 )
 
+func parseInt(str string) int {
+	v, _ := strconv.Atoi(str)
+	return v
+}
+
+func parseFloat64(str string) float64 {
+	v, _ := strconv.ParseFloat(str, 64)
+	return v
+}
+
 func readData() ([]time.Time, []float64) {
 	var xvalues []time.Time
 	var yvalues []float64
-	util.ReadFileByLines("requests.csv", func(line string) {
+	chart.File.ReadByLines("requests.csv", func(line string) {
 		parts := strings.Split(line, ",")
-		year := util.ParseInt(parts[0])
-		month := util.ParseInt(parts[1])
-		day := util.ParseInt(parts[2])
-		hour := util.ParseInt(parts[3])
-		elapsedMillis := util.ParseFloat64(parts[4])
+		year := parseInt(parts[0])
+		month := parseInt(parts[1])
+		day := parseInt(parts[2])
+		hour := parseInt(parts[3])
+		elapsedMillis := parseFloat64(parts[4])
 		xvalues = append(xvalues, time.Date(year, time.Month(month), day, hour, 0, 0, 0, time.UTC))
 		yvalues = append(yvalues, elapsedMillis)
 	})
@@ -27,12 +37,12 @@ func readData() ([]time.Time, []float64) {
 
 func releases() []chart.GridLine {
 	return []chart.GridLine{
-		{Value: chart.TimeToFloat64(time.Date(2016, 8, 1, 9, 30, 0, 0, time.UTC))},
-		{Value: chart.TimeToFloat64(time.Date(2016, 8, 2, 9, 30, 0, 0, time.UTC))},
-		{Value: chart.TimeToFloat64(time.Date(2016, 8, 3, 9, 30, 0, 0, time.UTC))},
-		{Value: chart.TimeToFloat64(time.Date(2016, 8, 4, 9, 30, 0, 0, time.UTC))},
-		{Value: chart.TimeToFloat64(time.Date(2016, 8, 5, 9, 30, 0, 0, time.UTC))},
-		{Value: chart.TimeToFloat64(time.Date(2016, 8, 6, 9, 30, 0, 0, time.UTC))},
+		{Value: chart.Time.ToFloat64(time.Date(2016, 8, 1, 9, 30, 0, 0, time.UTC))},
+		{Value: chart.Time.ToFloat64(time.Date(2016, 8, 2, 9, 30, 0, 0, time.UTC))},
+		{Value: chart.Time.ToFloat64(time.Date(2016, 8, 3, 9, 30, 0, 0, time.UTC))},
+		{Value: chart.Time.ToFloat64(time.Date(2016, 8, 4, 9, 30, 0, 0, time.UTC))},
+		{Value: chart.Time.ToFloat64(time.Date(2016, 8, 5, 9, 30, 0, 0, time.UTC))},
+		{Value: chart.Time.ToFloat64(time.Date(2016, 8, 6, 9, 30, 0, 0, time.UTC))},
 	}
 }
 
@@ -81,9 +91,14 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 			Name:      "Elapsed Millis",
 			NameStyle: chart.StyleShow(),
 			Style:     chart.StyleShow(),
+			TickStyle: chart.Style{
+				TextRotationDegrees: 45.0,
+			},
 		},
 		XAxis: chart.XAxis{
-			Style:          chart.StyleShow(),
+			Style: chart.Style{
+				Show: true,
+			},
 			ValueFormatter: chart.TimeHourValueFormatter,
 			GridMajorStyle: chart.Style{
 				Show:        true,

_examples/stock_analysis/main.go

@@ -60,8 +60,8 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 		},
 	}
 
-	res.Header().Set("Content-Type", "image/svg+xml")
-	graph.Render(chart.SVG, res)
+	res.Header().Set("Content-Type", "image/png")
+	graph.Render(chart.PNG, res)
 }
 
 func xvalues() []time.Time {

_examples/text_rotation/main.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/wcharczuk/go-chart"
+	"github.com/wcharczuk/go-chart/drawing"
+)
+
+func drawChart(res http.ResponseWriter, req *http.Request) {
+	f, _ := chart.GetDefaultFont()
+	r, _ := chart.PNG(1024, 1024)
+
+	chart.Draw.Text(r, "Test", 64, 64, chart.Style{
+		FontColor: drawing.ColorBlack,
+		FontSize:  18,
+		Font:      f,
+	})
+
+	chart.Draw.Text(r, "Test", 64, 64, chart.Style{
+		FontColor:           drawing.ColorBlack,
+		FontSize:            18,
+		Font:                f,
+		TextRotationDegrees: 45.0,
+	})
+
+	tb := chart.Draw.MeasureText(r, "Test", chart.Style{
+		FontColor: drawing.ColorBlack,
+		FontSize:  18,
+		Font:      f,
+	}).Shift(64, 64)
+
+	tbc := tb.Corners().Rotate(45)
+
+	chart.Draw.BoxCorners(r, tbc, chart.Style{
+		StrokeColor: drawing.ColorRed,
+		StrokeWidth: 2,
+	})
+
+	tbcb := tbc.Box()
+	chart.Draw.Box(r, tbcb, chart.Style{
+		StrokeColor: drawing.ColorBlue,
+		StrokeWidth: 2,
+	})
+
+	res.Header().Set("Content-Type", "image/png")
+	r.Save(res)
+}
+
+func main() {
+	http.HandleFunc("/", drawChart)
+	http.ListenAndServe(":8080", nil)
+}

box.go

@@ -1,6 +1,9 @@
 package chart
 
-import "fmt"
+import (
+	"fmt"
+	"math"
+)
 
 // Box represents the main 4 dimensions of a box.
 type Box struct {
@@ -76,8 +79,8 @@ func (b Box) Height() int {
 
 // Center returns the center of the box
 func (b Box) Center() (x, y int) {
-	w, h := b.Width(), b.Height()
-	return b.Left + w>>1, b.Top + h>>1
+	w2, h2 := b.Width()>>1, b.Height()>>1
+	return b.Left + w2, b.Top + h2
 }
 
 // Aspect returns the aspect ratio of the box.
@@ -139,6 +142,16 @@ func (b Box) Shift(x, y int) Box {
 	}
 }
 
+// Corners returns the box as a set of corners.
+func (b Box) Corners() BoxCorners {
+	return BoxCorners{
+		TopLeft:     Point{b.Left, b.Top},
+		TopRight:    Point{b.Right, b.Top},
+		BottomRight: Point{b.Right, b.Bottom},
+		BottomLeft:  Point{b.Left, b.Bottom},
+	}
+}
+
 // Fit is functionally the inverse of grow.
 // Fit maintains the original aspect ratio of the `other` box,
 // but constrains it to the bounds of the target box.
@@ -219,3 +232,99 @@ func (b Box) OuterConstrain(bounds, other Box) Box {
 	}
 	return newBox
 }
+
+// BoxCorners is a box with independent corners.
+type BoxCorners struct {
+	TopLeft, TopRight, BottomRight, BottomLeft Point
+}
+
+// Box return the BoxCorners as a regular box.
+func (bc BoxCorners) Box() Box {
+	return Box{
+		Top:    Math.MinInt(bc.TopLeft.Y, bc.TopRight.Y),
+		Left:   Math.MinInt(bc.TopLeft.X, bc.BottomLeft.X),
+		Right:  Math.MaxInt(bc.TopRight.X, bc.BottomRight.X),
+		Bottom: Math.MaxInt(bc.BottomLeft.Y, bc.BottomRight.Y),
+	}
+}
+
+// Width returns the width
+func (bc BoxCorners) Width() int {
+	minLeft := Math.MinInt(bc.TopLeft.X, bc.BottomLeft.X)
+	maxRight := Math.MaxInt(bc.TopRight.X, bc.BottomRight.X)
+	return maxRight - minLeft
+}
+
+// Height returns the height
+func (bc BoxCorners) Height() int {
+	minTop := Math.MinInt(bc.TopLeft.Y, bc.TopRight.Y)
+	maxBottom := Math.MaxInt(bc.BottomLeft.Y, bc.BottomRight.Y)
+	return maxBottom - minTop
+}
+
+// Center returns the center of the box
+func (bc BoxCorners) Center() (x, y int) {
+
+	left := Math.MeanInt(bc.TopLeft.X, bc.BottomLeft.X)
+	right := Math.MeanInt(bc.TopRight.X, bc.BottomRight.X)
+	x = ((right - left) >> 1) + left
+
+	top := Math.MeanInt(bc.TopLeft.Y, bc.TopRight.Y)
+	bottom := Math.MeanInt(bc.BottomLeft.Y, bc.BottomRight.Y)
+	y = ((bottom - top) >> 1) + top
+
+	return
+}
+
+// Rotate rotates the box.
+func (bc BoxCorners) Rotate(thetaDegrees float64) BoxCorners {
+	cx, cy := bc.Center()
+
+	thetaRadians := Math.DegreesToRadians(thetaDegrees)
+
+	tlx, tly := Math.RotateCoordinate(cx, cy, bc.TopLeft.X, bc.TopLeft.Y, thetaRadians)
+	trx, try := Math.RotateCoordinate(cx, cy, bc.TopRight.X, bc.TopRight.Y, thetaRadians)
+	brx, bry := Math.RotateCoordinate(cx, cy, bc.BottomRight.X, bc.BottomRight.Y, thetaRadians)
+	blx, bly := Math.RotateCoordinate(cx, cy, bc.BottomLeft.X, bc.BottomLeft.Y, thetaRadians)
+
+	return BoxCorners{
+		TopLeft:     Point{tlx, tly},
+		TopRight:    Point{trx, try},
+		BottomRight: Point{brx, bry},
+		BottomLeft:  Point{blx, bly},
+	}
+}
+
+// Equals returns if the box equals another box.
+func (bc BoxCorners) Equals(other BoxCorners) bool {
+	return bc.TopLeft.Equals(other.TopLeft) &&
+		bc.TopRight.Equals(other.TopRight) &&
+		bc.BottomRight.Equals(other.BottomRight) &&
+		bc.BottomLeft.Equals(other.BottomLeft)
+}
+
+func (bc BoxCorners) String() string {
+	return fmt.Sprintf("BoxC{%s,%s,%s,%s}", bc.TopLeft.String(), bc.TopRight.String(), bc.BottomRight.String(), bc.BottomLeft.String())
+}
+
+// Point is an X,Y pair
+type Point struct {
+	X, Y int
+}
+
+// DistanceTo calculates the distance to another point.
+func (p Point) DistanceTo(other Point) float64 {
+	dx := math.Pow(float64(p.X-other.X), 2)
+	dy := math.Pow(float64(p.Y-other.Y), 2)
+	return math.Pow(dx+dy, 0.5)
+}
+
+// Equals returns if a point equals another point.
+func (p Point) Equals(other Point) bool {
+	return p.X == other.X && p.Y == other.Y
+}
+
+// String returns a string representation of the point.
+func (p Point) String() string {
+	return fmt.Sprintf("P{%d,%d}", p.X, p.Y)
+}

box_test.go

@@ -143,3 +143,46 @@ func TestBoxShift(t *testing.T) {
 	assert.Equal(11, shifted.Right)
 	assert.Equal(12, shifted.Bottom)
 }
+
+func TestBoxCenter(t *testing.T) {
+	assert := assert.New(t)
+
+	b := Box{
+		Top:    10,
+		Left:   10,
+		Right:  20,
+		Bottom: 30,
+	}
+	cx, cy := b.Center()
+	assert.Equal(15, cx)
+	assert.Equal(20, cy)
+}
+
+func TestBoxCornersCenter(t *testing.T) {
+	assert := assert.New(t)
+
+	bc := BoxCorners{
+		TopLeft:     Point{5, 5},
+		TopRight:    Point{15, 5},
+		BottomRight: Point{15, 15},
+		BottomLeft:  Point{5, 15},
+	}
+
+	cx, cy := bc.Center()
+	assert.Equal(10, cx)
+	assert.Equal(10, cy)
+}
+
+func TestBoxCornersRotate(t *testing.T) {
+	assert := assert.New(t)
+
+	bc := BoxCorners{
+		TopLeft:     Point{5, 5},
+		TopRight:    Point{15, 5},
+		BottomRight: Point{15, 15},
+		BottomLeft:  Point{5, 15},
+	}
+
+	rotated := bc.Rotate(45)
+	assert.True(rotated.TopLeft.Equals(Point{10, 3}), rotated.String())
+}

chart.go

@@ -102,12 +102,12 @@ func (c Chart) Render(rp RendererProvider, w io.Writer) error {
 
 	if c.hasAxes() {
 		xt, yt, yta = c.getAxesTicks(r, xr, yr, yra, xf, yf, yfa)
-		canvasBox = c.getAxisAdjustedCanvasBox(r, canvasBox, xr, yr, yra, xt, yt, yta)
+		canvasBox = c.getAxesAdjustedCanvasBox(r, canvasBox, xr, yr, yra, xt, yt, yta)
 		xr, yr, yra = c.setRangeDomains(canvasBox, xr, yr, yra)
 
 		// do a second pass in case things haven't settled yet.
 		xt, yt, yta = c.getAxesTicks(r, xr, yr, yra, xf, yf, yfa)
-		canvasBox = c.getAxisAdjustedCanvasBox(r, canvasBox, xr, yr, yra, xt, yt, yta)
+		canvasBox = c.getAxesAdjustedCanvasBox(r, canvasBox, xr, yr, yra, xt, yt, yta)
 		xr, yr, yra = c.setRangeDomains(canvasBox, xr, yr, yra)
 	}
 
@@ -320,7 +320,7 @@ func (c Chart) getAxesTicks(r Renderer, xr, yr, yar Range, xf, yf, yfa ValueForm
 	return
 }
 
-func (c Chart) getAxisAdjustedCanvasBox(r Renderer, canvasBox Box, xr, yr, yra Range, xticks, yticks, yticksAlt []Tick) Box {
+func (c Chart) getAxesAdjustedCanvasBox(r Renderer, canvasBox Box, xr, yr, yra Range, xticks, yticks, yticksAlt []Tick) Box {
 	axesOuterBox := canvasBox.Clone()
 	if c.XAxis.Style.Show {
 		axesBounds := c.XAxis.Measure(r, canvasBox, xr, c.styleDefaultsAxes(), xticks)

draw.go

@@ -140,6 +140,7 @@ func (d draw) HistogramSeries(r Renderer, canvasBox Box, xrange, yrange Range, s
 // 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)
+	defer r.ResetStyle()
 
 	textBox := r.MeasureText(label)
 	textWidth := textBox.Width()
@@ -168,6 +169,8 @@ func (d draw) MeasureAnnotation(r Renderer, canvasBox Box, style Style, lx, ly i
 // Annotation draws an anotation with a renderer.
 func (d draw) Annotation(r Renderer, canvasBox Box, style Style, lx, ly int, label string) {
 	style.GetTextOptions().WriteToRenderer(r)
+	defer r.ResetStyle()
+
 	textBox := r.MeasureText(label)
 	textWidth := textBox.Width()
 	halfTextHeight := textBox.Height() >> 1
@@ -209,7 +212,8 @@ func (d draw) Annotation(r Renderer, canvasBox Box, style Style, lx, ly int, lab
 
 // Box draws a box with a given style.
 func (d draw) Box(r Renderer, b Box, s Style) {
-	s.WriteToRenderer(r)
+	s.GetFillAndStrokeOptions().WriteToRenderer(r)
+	defer r.ResetStyle()
 
 	r.MoveTo(b.Left, b.Top)
 	r.LineTo(b.Right, b.Top)
@@ -219,19 +223,45 @@ func (d draw) Box(r Renderer, b Box, s Style) {
 	r.FillStroke()
 }
 
+func (d draw) BoxRotated(r Renderer, b Box, thetaDegrees float64, s Style) {
+	d.BoxCorners(r, b.Corners().Rotate(thetaDegrees), s)
+}
+
+func (d draw) BoxCorners(r Renderer, bc BoxCorners, s Style) {
+	s.GetFillAndStrokeOptions().WriteToRenderer(r)
+	defer r.ResetStyle()
+
+	r.MoveTo(bc.TopLeft.X, bc.TopLeft.Y)
+	r.LineTo(bc.TopRight.X, bc.TopRight.Y)
+	r.LineTo(bc.BottomRight.X, bc.BottomRight.Y)
+	r.LineTo(bc.BottomLeft.X, bc.BottomLeft.Y)
+	r.Close()
+	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)
+	defer r.ResetStyle()
+
 	r.Text(text, x, y)
 }
 
+func (d draw) MeasureText(r Renderer, text string, style Style) Box {
+	style.GetTextOptions().WriteToRenderer(r)
+	defer r.ResetStyle()
+
+	return r.MeasureText(text)
+}
+
 // TextWithin draws the text within a given box.
 func (d draw) TextWithin(r Renderer, text string, box Box, style Style) {
+	style.GetTextOptions().WriteToRenderer(r)
+	defer r.ResetStyle()
+
 	lines := Text.WrapFit(r, text, box.Width(), style)
 	linesBox := Text.MeasureLines(r, lines, style)
 
-	style.GetTextOptions().WriteToRenderer(r)
-
 	y := box.Top
 
 	switch style.GetTextVerticalAlign() {
@@ -252,7 +282,11 @@ func (d draw) TextWithin(r Renderer, text string, box Box, style Style) {
 		default:
 			tx = box.Left
 		}
+		if style.TextRotationDegrees == 0 {
 			ty = y + lineBox.Height()
+		} else {
+			ty = y
+		}
 
 		d.Text(r, line, tx, ty, style)
 		y += lineBox.Height() + style.GetTextLineSpacing()

file_util.go

@@ -0,0 +1,52 @@
+package chart
+
+import (
+	"bufio"
+	"io"
+	"os"
+
+	exception "github.com/blendlabs/go-exception"
+)
+
+var (
+	// File contains file utility functions
+	File = fileUtil{}
+)
+
+type fileUtil struct{}
+
+// ReadByLines reads a file and calls the handler for each line.
+func (fu fileUtil) ReadByLines(filePath string, handler func(line string)) error {
+	if f, err := os.Open(filePath); err == nil {
+		defer f.Close()
+
+		scanner := bufio.NewScanner(f)
+		for scanner.Scan() {
+			line := scanner.Text()
+			handler(line)
+		}
+	} else {
+		return exception.Wrap(err)
+	}
+	return nil
+}
+
+// ReadByChunks reads a file in `chunkSize` pieces, dispatched to the handler.
+func (fu fileUtil) ReadByChunks(filePath string, chunkSize int, handler func(line []byte)) error {
+	if f, err := os.Open(filePath); err == nil {
+		defer f.Close()
+
+		chunk := make([]byte, chunkSize)
+		for {
+			readBytes, err := f.Read(chunk)
+			if err == io.EOF {
+				break
+			}
+			readData := chunk[:readBytes]
+			handler(readData)
+		}
+	} else {
+		return exception.Wrap(err)
+	}
+	return nil
+}

legend.go

@@ -54,9 +54,7 @@ func Legend(c *Chart, userDefaults ...Style) Renderable {
 			Bottom: legend.Top + legendPadding.Top,
 		}
 
-		r.SetFont(legendStyle.GetFont())
-		r.SetFontColor(legendStyle.GetFontColor())
-		r.SetFontSize(legendStyle.GetFontSize())
+		legendStyle.GetTextOptions().WriteToRenderer(r)
 
 		// measure
 		labelCount := 0
@@ -79,6 +77,8 @@ func Legend(c *Chart, userDefaults ...Style) Renderable {
 
 		Draw.Box(r, legend, legendStyle)
 
+		legendStyle.GetTextOptions().WriteToRenderer(r)
+
 		ycursor := legendContent.Top
 		tx := legendContent.Left
 		legendCount := 0

market_hours_range.go

@@ -33,12 +33,12 @@ func (mhr MarketHoursRange) IsZero() bool {
 
 // GetMin returns the min value.
 func (mhr MarketHoursRange) GetMin() float64 {
-	return TimeToFloat64(mhr.Min)
+	return Time.ToFloat64(mhr.Min)
 }
 
 // GetMax returns the max value.
 func (mhr MarketHoursRange) GetMax() float64 {
-	return TimeToFloat64(mhr.GetEffectiveMax())
+	return Time.ToFloat64(mhr.GetEffectiveMax())
 }
 
 // GetEffectiveMax gets either the close on the max, or the max itself.
@@ -52,13 +52,13 @@ func (mhr MarketHoursRange) GetEffectiveMax() time.Time {
 
 // SetMin sets the min value.
 func (mhr *MarketHoursRange) SetMin(min float64) {
-	mhr.Min = Float64ToTime(min)
+	mhr.Min = Time.FromFloat64(min)
 	mhr.Min = mhr.Min.In(mhr.GetTimezone())
 }
 
 // SetMax sets the max value.
 func (mhr *MarketHoursRange) SetMax(max float64) {
-	mhr.Max = Float64ToTime(max)
+	mhr.Max = Time.FromFloat64(max)
 	mhr.Max = mhr.Max.In(mhr.GetTimezone())
 }
 
@@ -159,7 +159,7 @@ func (mhr *MarketHoursRange) makeTicks(vf ValueFormatter, times []time.Time) []T
 	ticks := make([]Tick, len(times))
 	for index, t := range times {
 		ticks[index] = Tick{
-			Value: TimeToFloat64(t),
+			Value: Time.ToFloat64(t),
 			Label: vf(t),
 		}
 	}
@@ -172,7 +172,7 @@ func (mhr MarketHoursRange) String() string {
 
 // Translate maps a given value into the ContinuousRange space.
 func (mhr MarketHoursRange) Translate(value float64) int {
-	valueTime := Float64ToTime(value)
+	valueTime := Time.FromFloat64(value)
 	valueTimeEastern := valueTime.In(Date.Eastern())
 	totalSeconds := Date.CalculateMarketSecondsBetween(mhr.Min, mhr.GetEffectiveMax(), mhr.GetMarketOpen(), mhr.GetMarketClose(), mhr.HolidayProvider)
 	valueDelta := Date.CalculateMarketSecondsBetween(mhr.Min, valueTimeEastern, mhr.GetMarketOpen(), mhr.GetMarketClose(), mhr.HolidayProvider)

market_hours_range_test.go

@@ -35,9 +35,9 @@ func TestMarketHoursRangeTranslate(t *testing.T) {
 
 	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)))
+	assert.Equal(0, r.Translate(Time.ToFloat64(r.Min)))
+	assert.Equal(400, r.Translate(Time.ToFloat64(weds)))
+	assert.Equal(1000, r.Translate(Time.ToFloat64(r.Max)))
 }
 
 func TestMarketHoursRangeGetTicks(t *testing.T) {
@@ -67,6 +67,6 @@ func TestMarketHoursRangeGetTicks(t *testing.T) {
 	ticks := ra.GetTicks(r, defaults, TimeValueFormatter)
 	assert.NotEmpty(ticks)
 	assert.Len(ticks, 5)
-	assert.NotEqual(TimeToFloat64(ra.Min), ticks[0].Value)
+	assert.NotEqual(Time.ToFloat64(ra.Min), ticks[0].Value)
 	assert.NotEmpty(ticks[0].Label)
 }

math_util.go

@@ -19,16 +19,6 @@ const (
 	_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{}
@@ -144,6 +134,16 @@ func (m mathUtil) AbsInt(value int) int {
 	return value
 }
 
+// Mean returns the mean of a set of values
+func (m mathUtil) Mean(values ...float64) float64 {
+	return m.Sum(values...) / float64(len(values))
+}
+
+// MeanInt returns the mean of a set of integer values.
+func (m mathUtil) MeanInt(values ...int) int {
+	return m.SumInt(values...) / len(values)
+}
+
 // Sum sums a set of values.
 func (m mathUtil) Sum(values ...float64) float64 {
 	var total float64
@@ -214,9 +214,18 @@ func (m mathUtil) DegreesToCompass(deg float64) float64 {
 }
 
 // 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))
+// by the radius and the theta.
+func (m mathUtil) CirclePoint(cx, cy int, radius, thetaRadians float64) (x, y int) {
+	x = cx + int(radius*math.Sin(thetaRadians))
+	y = cy - int(radius*math.Cos(thetaRadians))
+	return
+}
+
+func (m mathUtil) RotateCoordinate(cx, cy, x, y int, thetaRadians float64) (rx, ry int) {
+	tempX, tempY := float64(x-cx), float64(y-cy)
+	rotatedX := tempX*math.Cos(thetaRadians) - tempY*math.Sin(thetaRadians)
+	rotatedY := tempX*math.Sin(thetaRadians) + tempY*math.Cos(thetaRadians)
+	rx = int(rotatedX) + cx
+	ry = int(rotatedY) + cy
 	return
 }

math_util_test.go

@@ -160,3 +160,25 @@ func TestRadianAdd(t *testing.T) {
 	assert.Equal(_pi, Math.RadianAdd(_pi, _2pi))
 	assert.Equal(_pi, Math.RadianAdd(_pi, -_2pi))
 }
+
+func TestRotateCoordinate90(t *testing.T) {
+	assert := assert.New(t)
+
+	cx, cy := 10, 10
+	x, y := 5, 10
+
+	rx, ry := Math.RotateCoordinate(cx, cy, x, y, Math.DegreesToRadians(90))
+	assert.Equal(10, rx)
+	assert.Equal(5, ry)
+}
+
+func TestRotateCoordinate45(t *testing.T) {
+	assert := assert.New(t)
+
+	cx, cy := 10, 10
+	x, y := 5, 10
+
+	rx, ry := Math.RotateCoordinate(cx, cy, x, y, Math.DegreesToRadians(45))
+	assert.Equal(7, rx)
+	assert.Equal(7, ry)
+}

raster_renderer.go

@@ -28,11 +28,16 @@ type rasterRenderer struct {
 	i  *image.RGBA
 	gc *drawing.RasterGraphicContext
 
-	rotateRadians float64
+	rotateRadians *float64
 
 	s Style
 }
 
+func (rr *rasterRenderer) ResetStyle() {
+	rr.s = Style{Font: rr.s.Font}
+	rr.ClearTextRotation()
+}
+
 // GetDPI returns the dpi.
 func (rr *rasterRenderer) GetDPI() float64 {
 	return rr.gc.GetDPI()
@@ -177,35 +182,40 @@ func (rr *rasterRenderer) MeasureText(body string) Box {
 		t = 0
 	}
 
-	return Box{
+	textBox := Box{
 		Top:    int(math.Ceil(t)),
 		Left:   int(math.Ceil(l)),
 		Right:  int(math.Ceil(r)),
 		Bottom: int(math.Ceil(b)),
 	}
+	if rr.rotateRadians == nil {
+		return textBox
+	}
+
+	return textBox.Corners().Rotate(Math.RadiansToDegrees(*rr.rotateRadians)).Box()
 }
 
 // SetTextRotation sets a text rotation.
 func (rr *rasterRenderer) SetTextRotation(radians float64) {
-	rr.rotateRadians = radians
+	rr.rotateRadians = &radians
 }
 
 func (rr *rasterRenderer) getCoords(x, y int) (xf, yf int) {
-	if rr.rotateRadians == 0 {
+	if rr.rotateRadians == nil {
 		xf = x
 		yf = y
 		return
 	}
 
 	rr.gc.Translate(float64(x), float64(y))
-	rr.gc.Rotate(rr.rotateRadians)
+	rr.gc.Rotate(*rr.rotateRadians)
 	return
 }
 
 // ClearTextRotation clears text rotation.
 func (rr *rasterRenderer) ClearTextRotation() {
 	rr.gc.SetMatrixTransform(drawing.NewIdentityMatrix())
-	rr.rotateRadians = 0
+	rr.rotateRadians = nil
 }
 
 // Save implements the interface method.

renderer.go

@@ -9,6 +9,9 @@ import (
 
 // Renderer represents the basic methods required to draw a chart.
 type Renderer interface {
+	// ResetStyle should reset any style related settings on the renderer.
+	ResetStyle()
+
 	// GetDPI gets the DPI for the renderer.
 	GetDPI() float64
 

style.go

@@ -33,6 +33,7 @@ type Style struct {
 	TextVerticalAlign   TextVerticalAlign
 	TextWrap            TextWrap
 	TextLineSpacing     int
+	TextRotationDegrees float64 //0 is unset or normal
 }
 
 // IsZero returns if the object is set or not.
@@ -241,6 +242,16 @@ func (s Style) GetTextLineSpacing(defaults ...int) int {
 	return s.TextLineSpacing
 }
 
+// GetTextRotationDegrees returns the text rotation in degrees.
+func (s Style) GetTextRotationDegrees(defaults ...float64) float64 {
+	if s.TextRotationDegrees == 0 {
+		if len(defaults) > 0 {
+			return defaults[0]
+		}
+	}
+	return s.TextRotationDegrees
+}
+
 // WriteToRenderer passes the style's options to a renderer.
 func (s Style) WriteToRenderer(r Renderer) {
 	r.SetStrokeColor(s.GetStrokeColor())
@@ -250,6 +261,11 @@ func (s Style) WriteToRenderer(r Renderer) {
 	r.SetFont(s.GetFont())
 	r.SetFontColor(s.GetFontColor())
 	r.SetFontSize(s.GetFontSize())
+
+	r.ClearTextRotation()
+	if s.GetTextRotationDegrees() != 0 {
+		r.SetTextRotation(Math.DegreesToRadians(s.GetTextRotationDegrees()))
+	}
 }
 
 // WriteDrawingOptionsToRenderer passes just the drawing style options to a renderer.
@@ -281,6 +297,7 @@ func (s Style) InheritFrom(defaults Style) (final Style) {
 	final.TextVerticalAlign = s.GetTextVerticalAlign(defaults.TextVerticalAlign)
 	final.TextWrap = s.GetTextWrap(defaults.TextWrap)
 	final.TextLineSpacing = s.GetTextLineSpacing(defaults.TextLineSpacing)
+	final.TextRotationDegrees = s.GetTextRotationDegrees(defaults.TextRotationDegrees)
 	return
 }
 
@@ -320,5 +337,6 @@ func (s Style) GetTextOptions() Style {
 		TextVerticalAlign:   s.TextVerticalAlign,
 		TextWrap:            s.TextWrap,
 		TextLineSpacing:     s.TextLineSpacing,
+		TextRotationDegrees: s.TextRotationDegrees,
 	}
 }

time_series.go

@@ -30,14 +30,14 @@ func (ts TimeSeries) Len() int {
 
 // GetValue gets a value at a given index.
 func (ts TimeSeries) GetValue(index int) (x, y float64) {
-	x = TimeToFloat64(ts.XValues[index])
+	x = Time.ToFloat64(ts.XValues[index])
 	y = ts.YValues[index]
 	return
 }
 
 // GetLastValue gets the last value.
 func (ts TimeSeries) GetLastValue() (x, y float64) {
-	x = TimeToFloat64(ts.XValues[len(ts.XValues)-1])
+	x = Time.ToFloat64(ts.XValues[len(ts.XValues)-1])
 	y = ts.YValues[len(ts.YValues)-1]
 	return
 }

time_util.go

@@ -0,0 +1,20 @@
+package chart
+
+import "time"
+
+var (
+	// Time contains time utility functions.
+	Time = timeUtil{}
+)
+
+type timeUtil struct{}
+
+// TimeToFloat64 returns a float64 representation of a time.
+func (tu timeUtil) ToFloat64(t time.Time) float64 {
+	return float64(t.UnixNano())
+}
+
+// Float64ToTime returns a time from a float64.
+func (tu timeUtil) FromFloat64(tf float64) time.Time {
+	return time.Unix(0, int64(tf))
+}

value_formatter_test.go

@@ -11,7 +11,7 @@ func TestTimeValueFormatterWithFormat(t *testing.T) {
 	assert := assert.New(t)
 
 	d := time.Now()
-	di := TimeToFloat64(d)
+	di := Time.ToFloat64(d)
 	df := float64(di)
 
 	s := TimeValueFormatterWithFormat(d, DefaultDateFormat)

vector_renderer.go

@@ -32,11 +32,15 @@ type vectorRenderer struct {
 	b   *bytes.Buffer
 	c   *canvas
 	s   *Style
-	r   float64
 	p   []string
 	fc  *font.Drawer
 }
 
+func (vr *vectorRenderer) ResetStyle() {
+	vr.s = &Style{Font: vr.s.Font}
+	vr.fc = nil
+}
+
 // GetDPI returns the dpi.
 func (vr *vectorRenderer) GetDPI() float64 {
 	return vr.dpi
@@ -168,18 +172,22 @@ func (vr *vectorRenderer) MeasureText(body string) (box Box) {
 
 		box.Right = w
 		box.Bottom = int(drawing.PointsToPixels(vr.dpi, vr.s.FontSize))
+		if vr.c.textTheta == nil {
+			return
+		}
+		box = box.Corners().Rotate(Math.RadiansToDegrees(*vr.c.textTheta)).Box()
 	}
 	return
 }
 
 // SetTextRotation sets the text rotation.
 func (vr *vectorRenderer) SetTextRotation(radians float64) {
-	vr.c.r = radians
+	vr.c.textTheta = &radians
 }
 
 // ClearTextRotation clears the text rotation.
 func (vr *vectorRenderer) ClearTextRotation() {
-	vr.c.r = 0
+	vr.c.textTheta = nil
 }
 
 // Save saves the renderer's contents to a writer.
@@ -198,7 +206,7 @@ func newCanvas(w io.Writer) *canvas {
 type canvas struct {
 	w         io.Writer
 	dpi       float64
-	r      float64
+	textTheta *float64
 	width     int
 	height    int
 }
@@ -218,10 +226,10 @@ func (c *canvas) Path(d string, style Style) {
 }
 
 func (c *canvas) Text(x, y int, body string, style Style) {
-	if c.r == 0 {
+	if c.textTheta == nil {
 		c.w.Write([]byte(fmt.Sprintf(`<text x="%d" y="%d" style="%s">%s</text>`, x, y, c.styleAsSVG(style), body)))
 	} else {
-		transform := fmt.Sprintf(` transform="rotate(%0.2f,%d,%d)"`, Math.RadiansToDegrees(c.r), x, y)
+		transform := fmt.Sprintf(` transform="rotate(%0.2f,%d,%d)"`, Math.RadiansToDegrees(*c.textTheta), x, y)
 		c.w.Write([]byte(fmt.Sprintf(`<text x="%d" y="%d" style="%s"%s>%s</text>`, x, y, c.styleAsSVG(style), transform, body)))
 	}
 }

xaxis.go

@@ -9,11 +9,13 @@ import (
 type XAxis struct {
 	Name      string
 	NameStyle Style
+
 	Style          Style
 	ValueFormatter ValueFormatter
 	Range          Range
-	Ticks          []Tick
 
+	TickStyle    Style
+	Ticks        []Tick
 	TickPosition TickPosition
 
 	GridLines      []GridLine
@@ -68,20 +70,20 @@ func (xa XAxis) GetGridLines(ticks []Tick) []GridLine {
 
 // Measure returns the bounds of the axis.
 func (xa XAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, ticks []Tick) Box {
-	tickStyle := xa.Style.InheritFrom(defaults)
+	tickStyle := xa.TickStyle.InheritFrom(xa.Style.InheritFrom(defaults))
 	sort.Sort(Ticks(ticks))
 
 	tp := xa.GetTickPosition()
 
+	var ltx, rtx int
+	var tx, ty int
 	var left, right, bottom = math.MaxInt32, 0, 0
 	for index, t := range ticks {
 		v := t.Value
-		tickStyle.GetTextOptions().WriteToRenderer(r)
-		tb := r.MeasureText(t.Label)
+		tb := Draw.MeasureText(r, t.Label, tickStyle.GetTextOptions())
 
-		var ltx, rtx int
-		tx := canvasBox.Left + ra.Translate(v)
-		ty := canvasBox.Bottom + DefaultXAxisMargin + tb.Height()
+		tx = canvasBox.Left + ra.Translate(v)
+		ty = canvasBox.Bottom + DefaultXAxisMargin + tb.Height()
 		switch tp {
 		case TickPositionUnderTick, TickPositionUnset:
 			ltx = tx - tb.Width()>>1
@@ -101,7 +103,7 @@ func (xa XAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 	}
 
 	if xa.NameStyle.Show && len(xa.Name) > 0 {
-		tb := r.MeasureText(xa.Name)
+		tb := Draw.MeasureText(r, xa.Name, xa.NameStyle.InheritFrom(defaults))
 		bottom += DefaultXAxisMargin + tb.Height()
 	}
 
@@ -115,7 +117,7 @@ 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) {
-	tickStyle := xa.Style.InheritFrom(defaults)
+	tickStyle := xa.TickStyle.InheritFrom(xa.Style.InheritFrom(defaults))
 
 	tickStyle.GetStrokeOptions().WriteToRenderer(r)
 	r.MoveTo(canvasBox.Left, canvasBox.Bottom)
@@ -139,25 +141,31 @@ func (xa XAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 		r.LineTo(tx, canvasBox.Bottom+DefaultVerticalTickHeight)
 		r.Stroke()
 
-		tickStyle.GetTextOptions().WriteToRenderer(r)
-		tb := r.MeasureText(t.Label)
+		tickWithAxisStyle := xa.TickStyle.InheritFrom(xa.Style.InheritFrom(defaults))
+		tb := Draw.MeasureText(r, t.Label, tickWithAxisStyle)
 
 		switch tp {
 		case TickPositionUnderTick, TickPositionUnset:
+			if tickStyle.TextRotationDegrees == 0 {
+				tx = tx - tb.Width()>>1
 				ty = canvasBox.Bottom + DefaultXAxisMargin + tb.Height()
-			r.Text(t.Label, tx-tb.Width()>>1, ty)
+			} else {
+				ty = canvasBox.Bottom + (2 * DefaultXAxisMargin)
+			}
+			Draw.Text(r, t.Label, tx, ty, tickWithAxisStyle)
 			maxTextHeight = Math.MaxInt(maxTextHeight, tb.Height())
 			break
 		case TickPositionBetweenTicks:
 			if index > 0 {
 				llx := ra.Translate(ticks[index-1].Value)
 				ltx := canvasBox.Left + llx
-				finalTickStyle := tickStyle.InheritFrom(Style{TextHorizontalAlign: TextHorizontalAlignCenter})
+				finalTickStyle := tickWithAxisStyle.InheritFrom(Style{TextHorizontalAlign: TextHorizontalAlignCenter})
+
 				Draw.TextWithin(r, t.Label, Box{
 					Left:   ltx,
 					Right:  tx,
 					Top:    canvasBox.Bottom + DefaultXAxisMargin,
-					Bottom: canvasBox.Bottom + DefaultXAxisMargin + tb.Height(),
+					Bottom: canvasBox.Bottom + DefaultXAxisMargin,
 				}, finalTickStyle)
 
 				ftb := Text.MeasureLines(r, Text.WrapFit(r, t.Label, tx-ltx, finalTickStyle), finalTickStyle)
@@ -169,11 +177,10 @@ func (xa XAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 
 	nameStyle := xa.NameStyle.InheritFrom(defaults)
 	if xa.NameStyle.Show && len(xa.Name) > 0 {
-		nameStyle.GetTextOptions().WriteToRenderer(r)
-		tb := r.MeasureText(xa.Name)
+		tb := Draw.MeasureText(r, xa.Name, nameStyle)
 		tx := canvasBox.Right - (canvasBox.Width()>>1 + tb.Width()>>1)
 		ty := canvasBox.Bottom + DefaultXAxisMargin + maxTextHeight + DefaultXAxisMargin + tb.Height()
-		r.Text(xa.Name, tx, ty)
+		Draw.Text(r, xa.Name, tx, ty, nameStyle)
 	}
 
 	if xa.GridMajorStyle.Show || xa.GridMinorStyle.Show {

yaxis.go

@@ -20,9 +20,10 @@ type YAxis struct {
 	ValueFormatter ValueFormatter
 	Range          Range
 
+	TickStyle Style
 	Ticks     []Tick
-	GridLines []GridLine
 
+	GridLines      []GridLine
 	GridMajorStyle Style
 	GridMinorStyle Style
 }
@@ -42,6 +43,11 @@ func (ya YAxis) GetStyle() Style {
 	return ya.Style
 }
 
+// GetTickStyle returns the tick style.
+func (ya YAxis) GetTickStyle() Style {
+	return ya.TickStyle
+}
+
 // GetTicks returns the ticks for a series.
 // The coalesce priority is:
 // 	- User Supplied Ticks (i.e. Ticks array on the axis itself).
@@ -68,8 +74,6 @@ func (ya YAxis) GetGridLines(ticks []Tick) []GridLine {
 
 // Measure returns the bounds of the axis.
 func (ya YAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, ticks []Tick) Box {
-	ya.Style.InheritFrom(defaults).WriteToRenderer(r)
-
 	sort.Sort(Ticks(ticks))
 
 	var tx int
@@ -79,6 +83,7 @@ func (ya YAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 		tx = canvasBox.Left - DefaultYAxisMargin
 	}
 
+	ya.TickStyle.InheritFrom(ya.Style.InheritFrom(defaults)).WriteToRenderer(r)
 	var minx, maxx, miny, maxy = math.MaxInt32, 0, math.MaxInt32, 0
 	var maxTextHeight int
 	for _, t := range ticks {
@@ -86,14 +91,13 @@ func (ya YAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 		ly := canvasBox.Bottom - ra.Translate(v)
 
 		tb := r.MeasureText(t.Label)
+		tbh2 := tb.Height() >> 1
 		finalTextX := tx
 		if ya.AxisType == YAxisSecondary {
 			finalTextX = tx - tb.Width()
 		}
 
-		if tb.Height() > maxTextHeight {
-			maxTextHeight = tb.Height()
-		}
+		maxTextHeight = Math.MaxInt(tb.Height(), maxTextHeight)
 
 		if ya.AxisType == YAxisPrimary {
 			minx = canvasBox.Right
@@ -102,8 +106,9 @@ func (ya YAxis) Measure(r Renderer, canvasBox Box, ra Range, defaults Style, tic
 			minx = Math.MinInt(minx, finalTextX)
 			maxx = Math.MaxInt(maxx, tx)
 		}
-		miny = Math.MinInt(miny, ly-tb.Height()>>1)
-		maxy = Math.MaxInt(maxy, ly+tb.Height()>>1)
+
+		miny = Math.MinInt(miny, ly-tbh2)
+		maxy = Math.MaxInt(maxy, ly+tbh2)
 	}
 
 	if ya.NameStyle.Show && len(ya.Name) > 0 {
@@ -120,11 +125,12 @@ 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) {
-	ya.Style.InheritFrom(defaults).WriteToRenderer(r)
+	tickStyle := ya.TickStyle.InheritFrom(ya.Style.InheritFrom(defaults))
+	tickStyle.WriteToRenderer(r)
 
 	sort.Sort(Ticks(ticks))
 
-	sw := ya.Style.GetStrokeWidth(defaults.StrokeWidth)
+	sw := tickStyle.GetStrokeWidth(defaults.StrokeWidth)
 
 	var lx int
 	var tx int
@@ -141,23 +147,30 @@ func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 	r.Stroke()
 
 	var maxTextWidth int
+	var finalTextX, finalTextY int
 	for _, t := range ticks {
 		v := t.Value
 		ly := canvasBox.Bottom - ra.Translate(v)
 
-		tb := r.MeasureText(t.Label)
+		tb := Draw.MeasureText(r, t.Label, tickStyle)
 
 		if tb.Width() > maxTextWidth {
 			maxTextWidth = tb.Width()
 		}
 
-		finalTextX := tx
-		finalTextY := ly + tb.Height()>>1
 		if ya.AxisType == YAxisSecondary {
 			finalTextX = tx - tb.Width()
+		} else {
+			finalTextX = tx
 		}
 
-		r.Text(t.Label, finalTextX, finalTextY)
+		if tickStyle.TextRotationDegrees == 0 {
+			finalTextY = ly + tb.Height()>>1
+		} else {
+			finalTextY = ly
+		}
+
+		tickStyle.WriteToRenderer(r)
 
 		r.MoveTo(lx, ly)
 		if ya.AxisType == YAxisPrimary {
@@ -166,15 +179,14 @@ func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 			r.LineTo(lx-DefaultHorizontalTickWidth, ly)
 		}
 		r.Stroke()
+
+		Draw.Text(r, t.Label, finalTextX, finalTextY, tickStyle)
 	}
 
-	nameStyle := ya.NameStyle.InheritFrom(defaults)
+	nameStyle := ya.NameStyle.InheritFrom(defaults.InheritFrom(Style{TextRotationDegrees: 90}))
 	if ya.NameStyle.Show && len(ya.Name) > 0 {
 		nameStyle.GetTextOptions().WriteToRenderer(r)
-
-		r.SetTextRotation(Math.DegreesToRadians(90))
-
-		tb := r.MeasureText(ya.Name)
+		tb := Draw.MeasureText(r, ya.Name, nameStyle)
 
 		var tx int
 		if ya.AxisType == YAxisPrimary {
@@ -183,10 +195,9 @@ func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 			tx = canvasBox.Left - (DefaultYAxisMargin + int(sw) + maxTextWidth + DefaultYAxisMargin)
 		}
 
-		ty := canvasBox.Bottom - (canvasBox.Height()>>1 + tb.Width()>>1)
+		ty := canvasBox.Top + (canvasBox.Height()>>1 + tb.Width()>>1)
 
-		r.Text(ya.Name, tx, ty)
-		r.ClearTextRotation()
+		Draw.Text(r, ya.Name, tx, ty, nameStyle)
 	}
 
 	if ya.Zero.Style.Show {