SVG!

chart.go

@@ -191,7 +191,7 @@ func (c Chart) initRanges(canvasBox Box) (xrange Range, yrange Range) {
 func (c Chart) drawBackground(r Renderer) {
 	r.SetFillColor(c.Background.GetFillColor(DefaultBackgroundColor))
 	r.SetStrokeColor(c.Background.GetStrokeColor(DefaultBackgroundStrokeColor))
-	r.SetLineWidth(c.Background.GetStrokeWidth(DefaultStrokeWidth))
+	r.SetStrokeWidth(c.Background.GetStrokeWidth(DefaultStrokeWidth))
 	r.MoveTo(0, 0)
 	r.LineTo(c.Width, 0)
 	r.LineTo(c.Width, c.Height)
@@ -204,7 +204,7 @@ func (c Chart) drawBackground(r Renderer) {
 func (c Chart) drawCanvas(r Renderer, canvasBox Box) {
 	r.SetFillColor(c.Canvas.GetFillColor(DefaultCanvasColor))
 	r.SetStrokeColor(c.Canvas.GetStrokeColor(DefaultCanvasStrokColor))
-	r.SetLineWidth(c.Canvas.GetStrokeWidth(DefaultStrokeWidth))
+	r.SetStrokeWidth(c.Canvas.GetStrokeWidth(DefaultStrokeWidth))
 	r.MoveTo(canvasBox.Left, canvasBox.Top)
 	r.LineTo(canvasBox.Right, canvasBox.Top)
 	r.LineTo(canvasBox.Right, canvasBox.Bottom)
@@ -217,7 +217,7 @@ func (c Chart) drawCanvas(r Renderer, canvasBox Box) {
 func (c Chart) drawAxes(r Renderer, canvasBox Box, xrange, yrange Range) {
 	if c.Axes.Show {
 		r.SetStrokeColor(c.Axes.GetStrokeColor(DefaultAxisColor))
-		r.SetLineWidth(c.Axes.GetStrokeWidth(DefaultStrokeWidth))
+		r.SetStrokeWidth(c.Axes.GetStrokeWidth(DefaultStrokeWidth))
 		r.MoveTo(canvasBox.Left, canvasBox.Bottom)
 		r.LineTo(canvasBox.Right, canvasBox.Bottom)
 		r.LineTo(canvasBox.Right, canvasBox.Top)
@@ -295,7 +295,7 @@ func (c Chart) drawXAxisLabels(r Renderer, canvasBox Box, xrange Range) {
 
 func (c Chart) drawSeries(r Renderer, canvasBox Box, index int, s Series, xrange, yrange Range) {
 	r.SetStrokeColor(s.GetStyle().GetStrokeColor(GetDefaultSeriesStrokeColor(index)))
-	r.SetLineWidth(s.GetStyle().GetStrokeWidth(DefaultStrokeWidth))
+	r.SetStrokeWidth(s.GetStyle().GetStrokeWidth(DefaultStrokeWidth))
 
 	if s.Len() == 0 {
 		return
@@ -366,7 +366,7 @@ func (c Chart) drawFinalValueLabel(r Renderer, canvasBox Box, index int, s Serie
 		//draw the shape...
 		r.SetFillColor(c.FinalValueLabel.GetFillColor(DefaultFinalLabelBackgroundColor))
 		r.SetStrokeColor(c.FinalValueLabel.GetStrokeColor(s.GetStyle().GetStrokeColor(GetDefaultSeriesStrokeColor(index))))
-		r.SetLineWidth(c.FinalValueLabel.GetStrokeWidth(DefaultAxisLineWidth))
+		r.SetStrokeWidth(c.FinalValueLabel.GetStrokeWidth(DefaultAxisLineWidth))
 		r.MoveTo(cx, ly)
 		r.LineTo(ltlx, ltly)
 		r.LineTo(ltrx, ltry)

raster_renderer.go

@@ -21,7 +21,7 @@ func PNG(width, height int) Renderer {
 	}
 }
 
-// RasterRenderer renders chart commands to a bitmap.
+// rasterRenderer renders chart commands to a bitmap.
 type rasterRenderer struct {
 	i  *image.RGBA
 	gc *drawing.GraphicContext
@@ -43,7 +43,7 @@ func (rr *rasterRenderer) SetFillColor(c color.RGBA) {
 }
 
 // SetLineWidth implements the interface method.
-func (rr *rasterRenderer) SetLineWidth(width float64) {
+func (rr *rasterRenderer) SetStrokeWidth(width float64) {
 	rr.gc.SetLineWidth(width)
 }
 
@@ -115,7 +115,7 @@ func (rr *rasterRenderer) Text(body string, x, y int) {
 	rr.gc.Fill()
 }
 
-// MeasureText implements the interface method.
+// MeasureText uses the truetype font drawer to measure the width of text.
 func (rr *rasterRenderer) MeasureText(body string) int {
 	if rr.fc == nil && rr.font != nil {
 		rr.fc = &font.Drawer{

renderer.go

@@ -18,8 +18,8 @@ type Renderer interface {
 	// SetFillColor sets the current fill color.
 	SetFillColor(color.RGBA)
 
-	// SetLineWidth sets the stroke line width.
+	// SetStrokeWidth sets the stroke width.
-	SetLineWidth(width float64)
+	SetStrokeWidth(width float64)
 
 	// MoveTo moves the cursor to a given point.
 	MoveTo(x, y int)

style.go

@@ -1,6 +1,10 @@
 package chart
 
-import "image/color"
+import (
+	"fmt"
+	"image/color"
+	"strings"
+)
 
 // Style is a simple style set.
 type Style struct {
@@ -72,3 +76,37 @@ func (s Style) GetFontColor(defaults ...color.RGBA) color.RGBA {
 	}
 	return s.FontColor
 }
+
+// SVG returns the style as a svg style string.
+func (s Style) SVG() 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 !ColorIsZero(sc) {
+		strokeText = "stroke:" + ColorAsString(sc)
+	}
+
+	fillText := "fill:none"
+	if !ColorIsZero(fc) {
+		fillText = "fill:" + ColorAsString(fc)
+	}
+
+	fontSizeText := ""
+	if fs != 0 {
+		fontSizeText = "font-size:" + fmt.Sprintf("%.1f", fs)
+	}
+
+	if !ColorIsZero(fnc) {
+		fillText = "fill:" + ColorAsString(fnc)
+	}
+	return strings.Join([]string{strokeWidthText, strokeText, fillText, fontSizeText}, ";")
+}

testserver/main.go

@@ -14,7 +14,7 @@ func main() {
 	app.SetName("Chart Test Server")
 	app.SetLogger(web.NewStandardOutputLogger())
 	app.GET("/", func(rc *web.RequestContext) web.ControllerResult {
-		rc.Response.Header().Set("Content-Type", "image/png")
+		rc.Response.Header().Set("Content-Type", "image/svg+xml")
 		now := time.Now()
 		c := chart.Chart{
 			Title: "A Test Chart",
@@ -49,7 +49,7 @@ func main() {
 		}
 
 		buffer := bytes.NewBuffer([]byte{})
-		err := c.Render(chart.PNG, buffer)
+		err := c.Render(chart.SVG, buffer)
 		if err != nil {
 			return rc.API().InternalError(err)
 		}

util.go

@@ -13,7 +13,8 @@ func ColorIsZero(c color.RGBA) bool {
 
 // ColorAsString returns if a color.RGBA is unset or not.
 func ColorAsString(c color.RGBA) string {
-	return fmt.Sprintf("RGBA(%v,%v,%v,%v)", c.R, c.G, c.G, c.A)
+	a := float64(c.A) / float64(255)
+	return fmt.Sprintf("rgba(%v,%v,%v,%.1f)", c.R, c.G, c.B, a)
 }
 
 // MinAndMax returns both the min and max in one pass.

vector_renderer.go

@@ -1 +1,153 @@
 package chart
+
+import (
+	"bytes"
+	"fmt"
+	"image/color"
+	"io"
+	"strings"
+
+	"golang.org/x/image/font"
+
+	"github.com/ajstarks/svgo"
+	"github.com/golang/freetype/truetype"
+)
+
+// SVG returns a new png/raster renderer.
+func SVG(width, height int) Renderer {
+	buffer := bytes.NewBuffer([]byte{})
+	canvas := svg.New(buffer)
+	canvas.Start(width, height)
+	return &vectorRenderer{
+		b: buffer,
+		c: canvas,
+		s: &Style{},
+		p: []string{},
+	}
+}
+
+// vectorRenderer renders chart commands to a bitmap.
+type vectorRenderer struct {
+	b  *bytes.Buffer
+	c  *svg.SVG
+	s  *Style
+	f  *truetype.Font
+	p  []string
+	fc *font.Drawer
+}
+
+func (vr *vectorRenderer) SetStrokeColor(c color.RGBA) {
+	vr.s.StrokeColor = c
+}
+
+// SetFillColor implements the interface method.
+func (vr *vectorRenderer) SetFillColor(c color.RGBA) {
+	vr.s.FillColor = c
+}
+
+// SetLineWidth implements the interface method.
+func (vr *vectorRenderer) SetStrokeWidth(width float64) {
+	vr.s.StrokeWidth = width
+}
+
+// MoveTo implements the interface method.
+func (vr *vectorRenderer) MoveTo(x, y int) {
+	vr.p = append(vr.p, fmt.Sprintf("M %d %d", x, y))
+}
+
+// LineTo implements the interface method.
+func (vr *vectorRenderer) LineTo(x, y int) {
+	vr.p = append(vr.p, fmt.Sprintf("L %d %d", x, y))
+}
+
+func (vr *vectorRenderer) Close() {
+	vr.p = append(vr.p, fmt.Sprintf("Z"))
+}
+
+// Stroke draws the path with no fill.
+func (vr *vectorRenderer) Stroke() {
+	vr.s.FillColor = color.RGBA{}
+	vr.s.FontColor = color.RGBA{}
+	vr.drawPath()
+}
+
+// Fill draws the path with no stroke.
+func (vr *vectorRenderer) Fill() {
+	vr.s.StrokeColor = color.RGBA{}
+	vr.s.StrokeWidth = 0
+	vr.s.FontColor = color.RGBA{}
+	vr.drawPath()
+}
+
+// FillStroke draws the path with both fill and stroke.
+func (vr *vectorRenderer) FillStroke() {
+	vr.s.FontColor = color.RGBA{}
+	vr.drawPath()
+}
+
+func (vr *vectorRenderer) drawPath() {
+	vr.c.Path(strings.Join(vr.p, "\n"), vr.s.SVG())
+	vr.p = []string{}
+}
+
+// Circle implements the interface method.
+func (vr *vectorRenderer) Circle(radius float64, x, y int) {
+	vr.c.Circle(x, y, int(radius), vr.s.SVG())
+}
+
+// SetFont implements the interface method.
+func (vr *vectorRenderer) SetFont(f *truetype.Font) {
+	vr.f = f
+}
+
+// SetFontColor implements the interface method.
+func (vr *vectorRenderer) SetFontColor(c color.RGBA) {
+	vr.s.FontColor = c
+}
+
+// SetFontSize implements the interface method.
+func (vr *vectorRenderer) SetFontSize(size float64) {
+	vr.s.FontSize = size
+}
+
+func (vr *vectorRenderer) svgFontFace() string {
+	family := "sans-serif"
+	if vr.f != nil {
+		name := vr.f.Name(truetype.NameIDFontFamily)
+		if len(name) != 0 {
+			family = fmt.Sprintf(`'%s',%s`, name, family)
+		}
+	}
+	return fmt.Sprintf("font-family:%s", family)
+}
+
+// Text draws a text blob.
+func (vr *vectorRenderer) Text(body string, x, y int) {
+	vr.s.FillColor = color.RGBA{}
+	vr.s.StrokeColor = color.RGBA{}
+	vr.s.StrokeWidth = 0
+	vr.c.Text(x, y, body, vr.s.SVG()+";"+vr.svgFontFace())
+}
+
+// MeasureText uses the truetype font drawer to measure the width of text.
+func (vr *vectorRenderer) MeasureText(body string) int {
+	if vr.fc == nil && vr.f != nil {
+		vr.fc = &font.Drawer{
+			Face: truetype.NewFace(vr.f, &truetype.Options{
+				DPI:  DefaultDPI,
+				Size: vr.s.FontSize,
+			}),
+		}
+	}
+	if vr.fc != nil {
+		dimensions := vr.fc.MeasureString(body)
+		return dimensions.Floor()
+	}
+	return 0
+}
+
+func (vr *vectorRenderer) Save(w io.Writer) error {
+	vr.c.End()
+	_, err := w.Write(vr.b.Bytes())
+	return err
+}