SVG!

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
+}