refactoring

context.go

@@ -42,17 +42,24 @@ type Context struct {
 	path      raster.Path
 	start     fixed.Point26_6
 	lineWidth float64
-	capper    raster.Capper
+	lineCap   LineCap
-	joiner    raster.Joiner
+	lineJoin  LineJoin
 	fillRule  FillRule
 	fontFace  font.Face
 }
 
 func NewContext(width, height int) *Context {
-	im := image.NewRGBA(image.Rect(0, 0, width, height))
+	return NewContextForRGBA(image.NewRGBA(image.Rect(0, 0, width, height)))
+}
+
+func NewContextForImage(im image.Image) *Context {
+	return NewContextForRGBA(imageToRGBA(im))
+}
+
+func NewContextForRGBA(im *image.RGBA) *Context {
 	return &Context{
-		width:     width,
+		width:     im.Bounds().Size().X,
-		height:    height,
+		height:    im.Bounds().Size().Y,
 		im:        im,
 		color:     color.Transparent,
 		lineWidth: 1,
@@ -77,11 +84,42 @@ func (dc *Context) WriteToPNG(path string) error {
 	return writeToPNG(path, dc.im)
 }
 
-func (dc *Context) Paint() {
+func (dc *Context) SetLineWidth(lineWidth float64) {
-	draw.Draw(dc.im, dc.im.Bounds(), image.NewUniform(dc.color), image.ZP, draw.Src)
+	dc.lineWidth = lineWidth
 }
 
-func (dc *Context) SetSourceRGBA(r, g, b, a float64) {
+func (dc *Context) SetLineCap(lineCap LineCap) {
+	dc.lineCap = lineCap
+}
+
+func (dc *Context) SetLineJoin(lineJoin LineJoin) {
+	dc.lineJoin = lineJoin
+}
+
+func (dc *Context) SetFillRule(fillRule FillRule) {
+	dc.fillRule = fillRule
+}
+
+// Color Setters
+
+func (dc *Context) SetColor(c color.Color) {
+	dc.color = c
+}
+
+func (dc *Context) SetHexColor(x string) {
+	r, g, b := parseHexColor(x)
+	dc.SetRGB255(r, g, b)
+}
+
+func (dc *Context) SetRGBA255(r, g, b, a int) {
+	dc.color = color.NRGBA{uint8(r), uint8(g), uint8(b), uint8(a)}
+}
+
+func (dc *Context) SetRGB255(r, g, b int) {
+	dc.SetRGBA255(r, g, b, 255)
+}
+
+func (dc *Context) SetRGBA(r, g, b, a float64) {
 	dc.color = color.NRGBA{
 		uint8(r * 255),
 		uint8(g * 255),
@@ -90,37 +128,11 @@ func (dc *Context) SetSourceRGBA(r, g, b, a float64) {
 	}
 }
 
-func (dc *Context) SetSourceRGB(r, g, b float64) {
+func (dc *Context) SetRGB(r, g, b float64) {
-	dc.SetSourceRGBA(r, g, b, 1)
+	dc.SetRGBA(r, g, b, 1)
 }
 
-func (dc *Context) SetLineWidth(lineWidth float64) {
+// Path Manipulation
-	dc.lineWidth = lineWidth
-}
-
-func (dc *Context) SetLineCap(lineCap LineCap) {
-	switch lineCap {
-	case LineCapButt:
-		dc.capper = raster.ButtCapper
-	case LineCapRound:
-		dc.capper = raster.RoundCapper
-	case LineCapSquare:
-		dc.capper = raster.SquareCapper
-	}
-}
-
-func (dc *Context) SetLineJoin(lineJoin LineJoin) {
-	switch lineJoin {
-	case LineJoinBevel:
-		dc.joiner = raster.BevelJoiner
-	case LineJoinRound:
-		dc.joiner = raster.RoundJoiner
-	}
-}
-
-func (dc *Context) SetFillRule(fillRule FillRule) {
-	dc.fillRule = fillRule
-}
 
 func (dc *Context) MoveTo(x, y float64) {
 	dc.start = fp(x, y)
@@ -149,22 +161,40 @@ func (dc *Context) ClosePath() {
 	}
 }
 
-func (dc *Context) NewPath() {
+func (dc *Context) ClearPath() {
 	dc.path.Clear()
 }
 
+// Path Drawing
+
 func (dc *Context) StrokePreserve() {
+	var capper raster.Capper
+	switch dc.lineCap {
+	case LineCapButt:
+		capper = raster.ButtCapper
+	case LineCapRound:
+		capper = raster.RoundCapper
+	case LineCapSquare:
+		capper = raster.SquareCapper
+	}
+	var joiner raster.Joiner
+	switch dc.lineJoin {
+	case LineJoinBevel:
+		joiner = raster.BevelJoiner
+	case LineJoinRound:
+		joiner = raster.RoundJoiner
+	}
 	painter := raster.NewRGBAPainter(dc.im)
 	painter.SetColor(dc.color)
 	r := raster.NewRasterizer(dc.width, dc.height)
 	r.UseNonZeroWinding = true
-	r.AddStroke(dc.path, fi(dc.lineWidth), dc.capper, dc.joiner)
+	r.AddStroke(dc.path, fi(dc.lineWidth), capper, joiner)
 	r.Rasterize(painter)
 }
 
 func (dc *Context) Stroke() {
 	dc.StrokePreserve()
-	dc.NewPath()
+	dc.ClearPath()
 }
 
 func (dc *Context) FillPreserve() {
@@ -182,17 +212,29 @@ func (dc *Context) FillPreserve() {
 
 func (dc *Context) Fill() {
 	dc.FillPreserve()
-	dc.NewPath()
+	dc.ClearPath()
 }
 
 // Convenient Drawing Functions
 
+func (dc *Context) Clear() {
+	draw.Draw(dc.im, dc.im.Bounds(), image.NewUniform(dc.color), image.ZP, draw.Src)
+}
+
 func (dc *Context) DrawLine(x1, y1, x2, y2 float64) {
 	dc.MoveTo(x1, y1)
 	dc.LineTo(x2, y2)
 }
 
-func (dc *Context) DrawEllipseArc(x, y, rx, ry, angle1, angle2 float64) {
+func (dc *Context) DrawRectangle(x, y, w, h float64) {
+	dc.MoveTo(x, y)
+	dc.LineTo(x+w, y)
+	dc.LineTo(x+w, y+h)
+	dc.LineTo(x, y+h)
+	dc.LineTo(x, y)
+}
+
+func (dc *Context) DrawEllipticalArc(x, y, rx, ry, angle1, angle2 float64) {
 	const n = 16
 	for i := 0; i <= n; i++ {
 		p1 := float64(i+0) / n
@@ -215,15 +257,15 @@ func (dc *Context) DrawEllipseArc(x, y, rx, ry, angle1, angle2 float64) {
 }
 
 func (dc *Context) DrawEllipse(x, y, rx, ry float64) {
-	dc.DrawEllipseArc(x, y, rx, ry, 0, 2*math.Pi)
+	dc.DrawEllipticalArc(x, y, rx, ry, 0, 2*math.Pi)
 }
 
 func (dc *Context) DrawArc(x, y, r, angle1, angle2 float64) {
-	dc.DrawEllipseArc(x, y, r, r, angle1, angle2)
+	dc.DrawEllipticalArc(x, y, r, r, angle1, angle2)
 }
 
 func (dc *Context) DrawCircle(x, y, r float64) {
-	dc.DrawEllipseArc(x, y, r, r, 0, 2*math.Pi)
+	dc.DrawEllipticalArc(x, y, r, r, 0, 2*math.Pi)
 }
 
 // Text Functions

examples/circle.go

@@ -4,12 +4,12 @@ import "github.com/fogleman/gg"
 
 func main() {
 	dc := gg.NewContext(1000, 1000)
-	dc.SetSourceRGB(1, 1, 1)
+	dc.SetRGB(1, 1, 1)
-	dc.Paint()
+	dc.Clear()
 	dc.DrawCircle(500, 500, 400)
-	dc.SetSourceRGBA(0, 0, 0, 0.25)
+	dc.SetRGBA(0, 0, 0, 0.25)
 	dc.FillPreserve()
-	dc.SetSourceRGB(0, 0, 0.5)
+	dc.SetRGB(0, 0, 0.5)
 	dc.SetLineWidth(8)
 	dc.Stroke()
 	dc.WriteToPNG("out.png")

examples/example0.go

@@ -4,16 +4,16 @@ import "github.com/fogleman/gg"
 
 func main() {
 	dc := gg.NewContext(256, 256)
-	dc.SetSourceRGBA(1, 0, 0, 0.3)
+	dc.SetRGBA(1, 0, 0, 0.3)
-	dc.Paint()
+	dc.Clear()
 	dc.MoveTo(20, 20)
 	dc.LineTo(236, 236)
 	dc.LineTo(236, 128)
 	dc.LineTo(20, 128)
 	dc.QuadraticTo(0, 64, 120, 20)
-	dc.SetSourceRGBA(1, 0, 0, 0.8)
+	dc.SetRGBA(1, 0, 0, 0.8)
 	dc.FillPreserve()
-	dc.SetSourceRGB(0, 0, 0)
+	dc.SetRGB(0, 0, 0)
 	dc.SetLineWidth(8)
 	dc.Stroke()
 	dc.WriteToPNG("out.png")

examples/lines.go

@@ -10,8 +10,8 @@ func main() {
 	const W = 1024
 	const H = 1024
 	dc := gg.NewContext(W, H)
-	dc.SetSourceRGB(0, 0, 0)
+	dc.SetRGB(0, 0, 0)
-	dc.Paint()
+	dc.Clear()
 	for i := 0; i < 1000; i++ {
 		x1 := rand.Float64() * W
 		y1 := rand.Float64() * H
@@ -22,10 +22,10 @@ func main() {
 		b := rand.Float64()
 		a := rand.Float64()*0.5 + 0.5
 		w := rand.Float64()*4 + 1
-		dc.SetSourceRGBA(r, g, b, a)
+		dc.SetRGBA(r, g, b, a)
 		dc.SetLineWidth(w)
-		dc.Stroke()
 		dc.DrawLine(x1, y1, x2, y2)
+		dc.Stroke()
 	}
 	dc.WriteToPNG("out.png")
 }

examples/star.go

@@ -23,17 +23,17 @@ func main() {
 	n := 5
 	points := Polygon(n, 512, 512, 400)
 	dc := gg.NewContext(1024, 1024)
-	dc.SetSourceRGB(1, 1, 1)
+	dc.SetHexColor("fff")
-	dc.Paint()
+	dc.Clear()
 	for i := 0; i < n+1; i++ {
 		index := (i * 2) % n
 		p := points[index]
 		dc.LineTo(p.X, p.Y)
 	}
-	dc.SetSourceRGBA(0, 0.5, 0, 1)
+	dc.SetRGBA(0, 0.5, 0, 1)
 	dc.SetFillRule(gg.FillRuleEvenOdd)
 	dc.FillPreserve()
-	dc.SetSourceRGBA(0, 1, 0, 0.5)
+	dc.SetRGBA(0, 1, 0, 0.5)
 	dc.SetLineWidth(16)
 	dc.Stroke()
 	dc.WriteToPNG("out.png")

examples/text.go

@@ -4,9 +4,9 @@ import "github.com/fogleman/gg"
 
 func main() {
 	dc := gg.NewContext(1000, 1000)
-	dc.SetSourceRGB(1, 1, 1)
+	dc.SetRGB(1, 1, 1)
-	dc.Paint()
+	dc.Clear()
-	dc.SetSourceRGB(0, 0, 0)
+	dc.SetRGB(0, 0, 0)
 	dc.LoadFontFace("/Library/Fonts/Impact.ttf", 96)
 	s := "Hello, world!"
 	w := dc.MeasureString(s)

util.go

@@ -1,10 +1,13 @@
 package gg
 
 import (
+	"fmt"
 	"image"
+	"image/draw"
 	"image/png"
 	"io/ioutil"
 	"os"
+	"strings"
 
 	"github.com/golang/freetype/truetype"
 
@@ -21,6 +24,28 @@ func writeToPNG(path string, im image.Image) error {
 	return png.Encode(file, im)
 }
 
+func imageToRGBA(src image.Image) *image.RGBA {
+	dst := image.NewRGBA(src.Bounds())
+	draw.Draw(dst, dst.Rect, src, image.ZP, draw.Src)
+	return dst
+}
+
+func parseHexColor(x string) (r, g, b int) {
+	x = strings.TrimPrefix(x, "#")
+	if len(x) == 3 {
+		format := "%1x%1x%1x"
+		fmt.Sscanf(x, format, &r, &g, &b)
+		r |= r << 4
+		g |= g << 4
+		b |= b << 4
+	}
+	if len(x) == 6 {
+		format := "%02x%02x%02x"
+		fmt.Sscanf(x, format, &r, &g, &b)
+	}
+	return
+}
+
 func fp(x, y float64) fixed.Point26_6 {
 	return fixed.Point26_6{fixed.Int26_6(x * 64), fixed.Int26_6(y * 64)}
 }