use draw.Image instead of image.Image

cmd/testX11draw.go

@@ -16,8 +16,7 @@ func main() {
 		return
 	}
 	screen := window.Screen()
-	if rgba, ok := screen.(*image.RGBA); ok {
+	gc := draw2d.NewImageGraphicContext(screen)
-		gc := draw2d.NewImageGraphicContext(rgba)
 	gc.SetStrokeColor(image.Black)
 	gc.SetFillColor(image.White)
 	gc.Clear()
@@ -30,7 +29,6 @@ func main() {
 		gc.Stroke()
 		gc.Restore() // Get back the unrotated state
 	}
-		fmt.Printf("This is an rgba image\n")
 
 	window.FlushImage()
 
@@ -56,7 +54,4 @@ func main() {
 			}
 		}
 	}
-	} else {
-		fmt.Printf("Not an RGBA image!\n")
-	}
 }

draw2d/Makefile

@@ -18,5 +18,6 @@ GOFILES=\
 	advanced_path.go\
 	vertex2d.go\
 	gc.go\
+	paint.go\
 
 include $(GOROOT)/src/Make.pkg

draw2d/draw2d.go

@@ -10,8 +10,14 @@ import (
 	"freetype-go.googlecode.com/hg/freetype/raster"
 )
 
+type Painter interface{
+	raster.Painter
+	SetColor(color image.Color)
+}
+
 type ImageGraphicContext struct {
-	PaintedImage     *image.RGBA
+	img     draw.Image
+	painter          Painter
 	fillRasterizer   *raster.Rasterizer
 	strokeRasterizer *raster.Rasterizer
 	freetype         *freetype.Context
@@ -39,10 +45,19 @@ type contextStack struct {
 /**
  * Create a new Graphic context from an image
  */
-func NewImageGraphicContext(pi *image.RGBA) *ImageGraphicContext {
+func NewImageGraphicContext(img draw.Image) *ImageGraphicContext {
 	gc := new(ImageGraphicContext)
-	gc.PaintedImage = pi
+	gc.img = img
-	width, height := gc.PaintedImage.Bounds().Dx(), gc.PaintedImage.Bounds().Dy()
+	switch selectImage := img.(type) {
+	case *image.RGBA:
+		gc.painter = raster.NewRGBAPainter(selectImage)
+	case *image.NRGBA:
+		gc.painter = NewNRGBAPainter(selectImage)
+	default:
+		panic("Image type not supported")
+	}
+	
+	width, height := gc.img.Bounds().Dx(), gc.img.Bounds().Dy()
 	gc.fillRasterizer = raster.NewRasterizer(width, height)
 	gc.strokeRasterizer = raster.NewRasterizer(width, height)
 
@@ -50,8 +65,8 @@ func NewImageGraphicContext(pi *image.RGBA) *ImageGraphicContext {
 	gc.defaultFontData = FontData{"luxi", FontFamilySans, FontStyleNormal}
 	gc.freetype = freetype.NewContext()
 	gc.freetype.SetDPI(gc.DPI)
-	gc.freetype.SetClip(pi.Bounds())
+	gc.freetype.SetClip(img.Bounds())
-	gc.freetype.SetDst(pi)
+	gc.freetype.SetDst(img)
 
 	gc.current = new(contextStack)
 
@@ -94,13 +109,13 @@ func (gc *ImageGraphicContext) Scale(sx, sy float64) {
 }
 
 func (gc *ImageGraphicContext) Clear() {
-	width, height := gc.PaintedImage.Bounds().Dx(), gc.PaintedImage.Bounds().Dy()
+	width, height := gc.img.Bounds().Dx(), gc.img.Bounds().Dy()
 	gc.ClearRect(0, 0, width, height)
 }
 
 func (gc *ImageGraphicContext) ClearRect(x1, y1, x2, y2 int) {
 	imageColor := image.NewColorImage(gc.current.fillColor)
-	draw.Draw(gc.PaintedImage, image.Rect(x1, y1, x2, y2), imageColor, image.ZP)
+	draw.Draw(gc.img, image.Rect(x1, y1, x2, y2), imageColor, image.ZP)
 }
 
 func (gc *ImageGraphicContext) SetStrokeColor(c image.Color) {
@@ -185,10 +200,8 @@ func (gc *ImageGraphicContext) Restore() {
 }
 
 func (gc *ImageGraphicContext) DrawImage(image image.Image) {
-	width := raster.Fix32(gc.PaintedImage.Bounds().Dx() * 256)
+	width := raster.Fix32(gc.img.Bounds().Dx() * 256)
-	height := raster.Fix32(gc.PaintedImage.Bounds().Dy() * 256)
+	height := raster.Fix32(gc.img.Bounds().Dy() * 256)
-
-	painter := raster.NewRGBAPainter(gc.PaintedImage)
 
 	p0 := raster.Point{0, 0}
 	p1 := raster.Point{0, 0}
@@ -209,8 +222,8 @@ func (gc *ImageGraphicContext) DrawImage(image image.Image) {
 			gc.fillRasterizer.Add1(p2)
 			gc.fillRasterizer.Add1(p3)
 			gc.fillRasterizer.Add1(p0)
-			painter.SetColor(image.At(int(i>>8), int(j>>8)))
+			gc.painter.SetColor(image.At(int(i>>8), int(j>>8)))
-			gc.fillRasterizer.Rasterize(painter)
+			gc.fillRasterizer.Rasterize(gc.painter)
 			gc.fillRasterizer.Clear()
 		}
 	}
@@ -302,9 +315,8 @@ func (gc *ImageGraphicContext) FillString(text string) (cursor float64) {
 
 
 func (gc *ImageGraphicContext) paint(rasterizer *raster.Rasterizer, color image.Color) {
-	painter := raster.NewRGBAPainter(gc.PaintedImage)
+	gc.painter.SetColor(color)
-	painter.SetColor(color)
+	rasterizer.Rasterize(gc.painter)
-	rasterizer.Rasterize(painter)
 	rasterizer.Clear()
 	gc.current.path = new(PathStorage)
 }

draw2d/paint.go

@@ -0,0 +1,94 @@
+// Copyright 2010 The draw2d Authors. All rights reserved.
+// created: 21/11/2010 by Laurent Le Goff
+package draw2d
+
+import (
+	"exp/draw"
+	"image"
+	"freetype-go.googlecode.com/hg/freetype/raster"
+)
+
+const M = 1<<16 - 1
+
+type NRGBAPainter struct {
+	// The image to compose onto.
+	Image *image.NRGBA
+	// The Porter-Duff composition operator.
+	Op draw.Op
+	// The 16-bit color to paint the spans.
+	cr, cg, cb, ca uint32
+}
+
+func min(a, b uint32) uint32 {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+// Paint satisfies the Painter interface by painting ss onto an image.RGBA.
+func (r *NRGBAPainter) Paint(ss []raster.Span, done bool) {
+	b := r.Image.Bounds()
+	for _, s := range ss {
+		if s.Y < b.Min.Y {
+			continue
+		}
+		if s.Y >= b.Max.Y {
+			return
+		}
+		if s.X0 < b.Min.X {
+			s.X0 = b.Min.X
+		}
+		if s.X1 > b.Max.X {
+			s.X1 = b.Max.X
+		}
+		if s.X0 >= s.X1 {
+			continue
+		}
+		base := s.Y * r.Image.Stride
+		p := r.Image.Pix[base+s.X0 : base+s.X1]
+		// This code is duplicated from drawGlyphOver in $GOROOT/src/pkg/exp/draw/draw.go.
+		// TODO(nigeltao): Factor out common code into a utility function, once the compiler
+		// can inline such function calls.
+		ma := s.A >> 16
+		if r.Op == draw.Over {
+			for i, nrgba := range p {
+				dr, dg, db, da := nrgba.RGBA()
+				a := M - (r.ca*ma)/M
+				da = (da*a + r.ca*ma) / M
+				if da != 0 {
+					dr = min(M, (dr*a+r.cr*ma)/da)
+					dg = min(M, (dg*a+r.cg*ma)/da)
+					db = min(M, (db*a+r.cb*ma)/da)
+				} else {
+					dr, dg, db = 0, 0, 0
+				}
+				p[i] = image.NRGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
+			}
+		} else {
+			for i, nrgba := range p {
+				dr, dg, db, da := nrgba.RGBA()
+				a := M - ma
+				da = (da*a + r.ca*ma) / M
+				if da != 0 {
+					dr = min(M, (dr*a+r.cr*ma)/da)
+					dg = min(M, (dg*a+r.cg*ma)/da)
+					db = min(M, (db*a+r.cb*ma)/da)
+				} else {
+					dr, dg, db = 0, 0, 0
+				}
+				p[i] = image.NRGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
+			}
+		}
+	}
+}
+
+// SetColor sets the color to paint the spans.
+func (r *NRGBAPainter) SetColor(c image.Color) {
+	r.cr, r.cg, r.cb, r.ca = c.RGBA()
+}
+
+// NewRGBAPainter creates a new RGBAPainter for the given image.
+func NewNRGBAPainter(m *image.NRGBA) *NRGBAPainter {
+	return &NRGBAPainter{Image: m}
+}