snapshot.

_examples/text_rotation/main.go

@@ -15,12 +15,30 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 		YAxis: chart.YAxis{
 			Style: chart.Style{
 				Show: true,
-				TextRotationDegrees: 45.0,
 			},
 			Range: &chart.ContinuousRange{
 				Min: 0.0,
 				Max: 4.0,
 			},
+			TickStyle: chart.Style{
+				TextRotationDegrees: 45.0,
+			},
+			Ticks: []chart.Tick{
+				{0.0, "0.00"},
+				{2.0, "2.00"},
+				{4.0, "4.00"},
+				{6.0, "6.00"},
+				{8.0, "Eight"},
+				{10.0, "Ten"},
+			},
+		},
+		XAxis: chart.XAxis{
+			Style: chart.Style{
+				Show: true,
+			},
+			TickStyle: chart.Style{
+				TextRotationDegrees: 45.0,
+			},
 			Ticks: []chart.Tick{
 				{0.0, "0.00"},
 				{2.0, "2.00"},
@@ -39,6 +57,20 @@ func drawChart(res http.ResponseWriter, req *http.Request) {
 	}
 
 	res.Header().Set("Content-Type", "image/png")
+	graph.Elements = []chart.Renderable{
+		func(r chart.Renderer, cb chart.Box, defaults chart.Style) {
+
+			b := chart.Box{50, 50, 90, 110}
+			chart.Draw.Box(r, b, chart.Style{
+				StrokeWidth: 2,
+				StrokeColor: chart.ColorBlue,
+			})
+			chart.Draw.Box(r, b.Rotate(chart.Math.DegreesToRadians(45)), chart.Style{
+				StrokeWidth: 2,
+				StrokeColor: chart.ColorRed,
+			})
+		},
+	}
 	graph.Render(chart.PNG, res)
 }
 

box.go

@@ -76,8 +76,8 @@ 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()
+	w2, h2 := b.Width()>>1, b.Height()>>1
-	return b.Left + w>>1, b.Top + h>>1
+	return b.Left + w2, b.Top + h2
 }
 
 // Aspect returns the aspect ratio of the box.
@@ -227,8 +227,8 @@ func (b Box) Rotate(radians float64) Box {
 	ltx, lty := Math.RotateCoordinate(cx, cy, b.Left, b.Top, radians)
 	rbx, rby := Math.RotateCoordinate(cx, cy, b.Right, b.Bottom, radians)
 	return Box{
-		Top:    lty,
 		Left:   ltx,
+		Top:    lty,
 		Right:  rbx,
 		Bottom: rby,
 	}

box_test.go

@@ -144,6 +144,20 @@ func TestBoxShift(t *testing.T) {
 	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 TestBoxRotate(t *testing.T) {
 	assert := assert.New(t)
 
@@ -156,6 +170,6 @@ func TestBoxRotate(t *testing.T) {
 	rotated := b.Rotate(Math.DegreesToRadians(45))
 	assert.Equal(1, rotated.Top)
 	assert.Equal(4, rotated.Left)
-	assert.Equal(11, rotated.Right)
+	assert.Equal(10, rotated.Right)
-	assert.Equal(15, rotated.Bottom)
+	assert.Equal(14, rotated.Bottom)
 }

math.go

@@ -223,9 +223,9 @@ func (m mathUtil) CirclePoint(cx, cy int, radius, thetaRadians float64) (x, y in
 
 func (m mathUtil) RotateCoordinate(cx, cy, x, y int, thetaRadians float64) (rx, ry int) {
 	tempX, tempY := float64(x-cx), float64(y-cy)
-	rotatedX := int(math.Ceil(tempX*math.Cos(thetaRadians) - tempY*math.Sin(thetaRadians)))
+	rotatedX := tempX*math.Cos(thetaRadians) - tempY*math.Sin(thetaRadians)
-	rotatedY := int(math.Ceil(tempX*math.Sin(thetaRadians) + tempY*math.Cos(thetaRadians)))
+	rotatedY := tempX*math.Sin(thetaRadians) + tempY*math.Cos(thetaRadians)
-	rx = rotatedX + cy
+	rx = int(rotatedX) + cy
-	ry = rotatedY + cy
+	ry = int(rotatedY) + cy
 	return
 }

math_test.go

@@ -161,13 +161,24 @@ func TestRadianAdd(t *testing.T) {
 	assert.Equal(_pi, Math.RadianAdd(_pi, -_2pi))
 }
 
-func TestRotateCoordinate(t *testing.T) {
+func TestRotateCoordinate90(t *testing.T) {
 	assert := assert.New(t)
 
 	cx, cy := 10, 10
-	x, y := 5, 5
+	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(10, rx)
+	assert.Equal(7, rx)
-	assert.Equal(3, ry)
+	assert.Equal(7, ry)
 }

raster_renderer.go

@@ -28,7 +28,7 @@ type rasterRenderer struct {
 	i  *image.RGBA
 	gc *drawing.RasterGraphicContext
 
-	rotateRadians float64
+	rotateRadians *float64
 
 	s Style
 }
@@ -183,34 +183,34 @@ func (rr *rasterRenderer) MeasureText(body string) Box {
 		Right:  int(math.Ceil(r)),
 		Bottom: int(math.Ceil(b)),
 	}
-	if rr.rotateRadians == 0 {
+	if rr.rotateRadians == nil {
 		return textBox
 	}
 
-	return textBox.Rotate(rr.rotateRadians)
+	return textBox.Rotate(*rr.rotateRadians)
 }
 
 // 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.

style.go

@@ -33,7 +33,7 @@ type Style struct {
 	TextVerticalAlign   TextVerticalAlign
 	TextWrap            TextWrap
 	TextLineSpacing     int
-	TextRotationDegrees float64
+	TextRotationDegrees float64 //0 is unset or normal
 }
 
 // IsZero returns if the object is set or not.
@@ -262,9 +262,8 @@ func (s Style) WriteToRenderer(r Renderer) {
 	r.SetFontColor(s.GetFontColor())
 	r.SetFontSize(s.GetFontSize())
 
-	if s.GetTextRotationDegrees() == 0 {
 	r.ClearTextRotation()
-	} else {
+	if s.GetTextRotationDegrees() != 0 {
 		r.SetTextRotation(Math.DegreesToRadians(s.GetTextRotationDegrees()))
 	}
 }

vector_renderer.go

@@ -32,7 +32,6 @@ type vectorRenderer struct {
 	b   *bytes.Buffer
 	c   *canvas
 	s   *Style
-	r   float64
 	p   []string
 	fc  *font.Drawer
 }
@@ -168,18 +167,22 @@ 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.Rotate(*vr.c.textTheta)
 	}
 	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 +201,7 @@ func newCanvas(w io.Writer) *canvas {
 type canvas struct {
 	w         io.Writer
 	dpi       float64
-	r      float64
+	textTheta *float64
 	width     int
 	height    int
 }
@@ -218,10 +221,10 @@ 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
@@ -139,7 +141,7 @@ 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)
+		xa.TickStyle.InheritFrom(xa.Style.InheritFrom(defaults)).WriteToRenderer(r)
 		tb := r.MeasureText(t.Label)
 
 		switch tp {

yaxis.go

@@ -22,8 +22,8 @@ type YAxis struct {
 
 	TickStyle Style
 	Ticks     []Tick
-	GridLines []GridLine
 
+	GridLines      []GridLine
 	GridMajorStyle Style
 	GridMinorStyle Style
 }
@@ -149,11 +149,10 @@ func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 
 	var maxTextWidth int
 	for _, t := range ticks {
+		ya.TickStyle.InheritFrom(ya.Style.InheritFrom(defaults)).WriteToRenderer(r)
 
 		v := t.Value
 		ly := canvasBox.Bottom - ra.Translate(v)
-
-		ya.TickStyle.InheritFrom(ya.Style.InheritFrom(defaults)).WriteToRenderer(r)
 		tb := r.MeasureText(t.Label)
 
 		if tb.Width() > maxTextWidth {
@@ -167,7 +166,8 @@ func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, defaults Style, tick
 		}
 
 		r.Text(t.Label, finalTextX, finalTextY)
-		r.ClearTextRotation()
+
+		ya.Style.InheritFrom(defaults).WriteToRenderer(r)
 
 		r.MoveTo(lx, ly)
 		if ya.AxisType == YAxisPrimary {