choose interpolation algorithm

cmd/testimage.go

@@ -17,19 +17,19 @@ func saveToPngFile(filePath string, m image.Image) {
 	f, err := os.Open(filePath, os.O_CREAT|os.O_WRONLY, 0600)
 	if err != nil {
 		log.Println(err)
-		os.Exit(1)
+		return
 	}
 	defer f.Close()
 	b := bufio.NewWriter(f)
 	err = png.Encode(b, m)
 	if err != nil {
 		log.Println(err)
-		os.Exit(1)
+		return
 	}
 	err = b.Flush()
 	if err != nil {
 		log.Println(err)
-		os.Exit(1)
+		return
 	}
 	fmt.Printf("Wrote %s OK.\n", filePath)
 }
@@ -52,29 +52,20 @@ func loadFromPngFile(filePath string) image.Image {
 }
 
 
-func testBubble(gc draw2d.GraphicContext) {
-	gc.BeginPath()
-	gc.MoveTo(75, 25)
-	gc.QuadCurveTo(25, 25, 25, 62.5)
-	gc.QuadCurveTo(25, 100, 50, 100)
-	gc.QuadCurveTo(50, 120, 30, 125)
-	gc.QuadCurveTo(60, 120, 65, 100)
-	gc.QuadCurveTo(125, 100, 125, 62.5)
-	gc.QuadCurveTo(125, 25, 75, 25)
-	gc.Stroke()
-}
-
 func main() {
-
+	source := loadFromPngFile("../resource/image/TestAndroid.png")
-	source := loadFromPngFile("../resource/image/Varna_Railway_Station_HDR.png")
 	i := image.NewRGBA(1024, 768)
 	gc := draw2d.NewImageGraphicContext(i)
-	gc.Scale(2, 0.5)
+//	gc.Scale(2, 0.5)
-	//gc.Translate(75, 25)
+	gc.Translate(float64(source.Bounds().Dx()/2), float64(source.Bounds().Dy()/2))
 	gc.Rotate(30 * math.Pi / 180)
+	gc.Translate(float64(-source.Bounds().Dx()/2), float64(-source.Bounds().Dy()/2))
+	gc.Translate(75, 25)
 	lastTime := time.Nanoseconds()
 	gc.DrawImage(source)
 	dt := time.Nanoseconds() - lastTime
 	fmt.Printf("Draw image: %f ms\n", float64(dt)*1e-6)
 	saveToPngFile("../resource/result/TestDrawImage.png", i)
 }
+
+

draw2d/draw2d.go

@@ -200,7 +200,7 @@ func (gc *ImageGraphicContext) Restore() {
 }
 
 func (gc *ImageGraphicContext) DrawImage(img image.Image) {
-	DrawImage(img, gc.img, gc.current.tr, draw.Over, linearFilter)
+	DrawImage(img, gc.img, gc.current.tr, draw.Over, BilinearFilter)
 }
 
 func (gc *ImageGraphicContext) BeginPath() {

draw2d/math.go

@@ -21,3 +21,31 @@ func squareDistance(x1, y1, x2, y2 float64) float64 {
 	dy := y2 - y1
 	return dx*dx + dy*dy
 }
+
+func min(x, y float64) float64 {
+	if x < y {
+		return x
+	}
+	return y
+}
+
+func max(x, y float64) float64 {
+	if x > y {
+		return x
+	}
+	return y
+}
+
+func minMax(x, y float64) (min, max float64) {
+	if x > y {
+		return y, x
+	}
+	return x, y
+}
+
+func minUint32(a, b uint32) uint32 {
+	if a < b {
+		return a
+	}
+	return b
+}

draw2d/paint.go

@@ -19,13 +19,6 @@ type NRGBAPainter struct {
 	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()
@@ -57,9 +50,9 @@ func (r *NRGBAPainter) Paint(ss []raster.Span, done bool) {
 				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)
+					dr = minUint32(M, (dr*a+r.cr*ma)/da)
-					dg = min(M, (dg*a+r.cg*ma)/da)
+					dg = minUint32(M, (dg*a+r.cg*ma)/da)
-					db = min(M, (db*a+r.cb*ma)/da)
+					db = minUint32(M, (db*a+r.cb*ma)/da)
 				} else {
 					dr, dg, db = 0, 0, 0
 				}
@@ -71,9 +64,9 @@ func (r *NRGBAPainter) Paint(ss []raster.Span, done bool) {
 				a := M - ma
 				da = (da*a + r.ca*ma) / M
 				if da != 0 {
-					dr = min(M, (dr*a+r.cr*ma)/da)
+					dr = minUint32(M, (dr*a+r.cr*ma)/da)
-					dg = min(M, (dg*a+r.cg*ma)/da)
+					dg = minUint32(M, (dg*a+r.cg*ma)/da)
-					db = min(M, (db*a+r.cb*ma)/da)
+					db = minUint32(M, (db*a+r.cb*ma)/da)
 				} else {
 					dr, dg, db = 0, 0, 0
 				}

draw2d/rgba_interpolation.go

@@ -5,12 +5,13 @@ import (
 	"image"
 	"math"
 )
+
 type ImageFilter int
 
 const (
-	linearFilter ImageFilter = iota
+	LinearFilter ImageFilter = iota
-	bilinearFilter
+	BilinearFilter
-	bicubicFilter
+	BicubicFilter
 )
 
 //see http://pippin.gimp.org/image_processing/chap_resampling.html
@@ -59,8 +60,8 @@ func getColorCubicRow(img image.Image, x, y, offset float64) image.Color {
 	r1, g1, b1, a1 := c1.RGBA()
 	r2, g2, b2, a2 := c2.RGBA()
 	r3, g3, b3, a3 := c3.RGBA()
-	r, g, b, a := cubic(offset,float64(r0),float64(r1),float64(r2),float64(r3)), cubic(offset,float64(g0),float64(g1),float64(g2),float64(g3)), cubic(offset,float64(b0),float64(b1),float64(b2),float64(b3)), cubic(offset,float64(a0),float64(a1),float64(a2),float64(a3))
+	r, g, b, a := cubic(offset, float64(r0), float64(r1), float64(r2), float64(r3)), cubic(offset, float64(g0), float64(g1), float64(g2), float64(g3)), cubic(offset, float64(b0), float64(b1), float64(b2), float64(b3)), cubic(offset, float64(a0), float64(a1), float64(a2), float64(a3))
-  return image.RGBAColor{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
+	return image.RGBAColor{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
 }
 
 func getColorBicubic(img image.Image, x, y float64) image.Color {
@@ -77,15 +78,15 @@ func getColorBicubic(img image.Image, x, y float64) image.Color {
 	r1, g1, b1, a1 := c1.RGBA()
 	r2, g2, b2, a2 := c2.RGBA()
 	r3, g3, b3, a3 := c3.RGBA()
-	r, g, b, a := cubic(dy,float64(r0),float64(r1),float64(r2),float64(r3)), cubic(dy,float64(g0),float64(g1),float64(g2),float64(g3)), cubic(dy,float64(b0),float64(b1),float64(b2),float64(b3)), cubic(dy,float64(a0),float64(a1),float64(a2),float64(a3))
+	r, g, b, a := cubic(dy, float64(r0), float64(r1), float64(r2), float64(r3)), cubic(dy, float64(g0), float64(g1), float64(g2), float64(g3)), cubic(dy, float64(b0), float64(b1), float64(b2), float64(b3)), cubic(dy, float64(a0), float64(a1), float64(a2), float64(a3))
 	return image.RGBAColor{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
 }
 
-func cubic(offset,v0,v1,v2,v3 float64) uint32{
+func cubic(offset, v0, v1, v2, v3 float64) uint32 {
-  // offset is the offset of the sampled value between v1 and v2
+	// offset is the offset of the sampled value between v1 and v2
-   return   uint32((((( -7 * v0 + 21 * v1 - 21 * v2 + 7 * v3 ) * offset +
+	return uint32(((((-7*v0+21*v1-21*v2+7*v3)*offset+
-               ( 15 * v0 - 36 * v1 + 27 * v2 - 6 * v3 ) ) * offset +
+		(15*v0-36*v1+27*v2-6*v3))*offset+
-               ( -9 * v0 + 9 * v2 ) ) * offset + (v0 + 16 * v1 + v2) ) / 18.0);
+		(-9*v0+9*v2))*offset + (v0 + 16*v1 + v2)) / 18.0)
 }
 
 func compose(c1, c2 image.Color) image.Color {
@@ -99,20 +100,42 @@ func compose(c1, c2 image.Color) image.Color {
 	return image.RGBAColor{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
 }
 
+
 func DrawImage(src image.Image, dest draw.Image, tr MatrixTransform, op draw.Op, filter ImageFilter) {
-	//width := float64(src.Bounds().Dx())
+	b := src.Bounds()
-	//height := float64(src.Bounds().Dy())
+	x0, y0, x1, y1 := float64(b.Min.X), float64(b.Min.Y), float64(b.Max.X), float64(b.Max.Y)
-	//tr.InverseTransform(&width, &height)
+	tr.TransformRectangle(&x0, &y0, &x1, &y1)
-	// TODO: find a x0, y0, x1, y1 that fits into dest 0, width, 0, height is too large
-	width := float64(dest.Bounds().Dx())
-	height:= float64(dest.Bounds().Dy())
 	var x, y, u, v float64
-	for x = 0; x < width; x++ {
+	for x = x0; x < x1; x++ {
-		for y = 0; y < height; y++ {
+		for y = y0; y < y1; y++ {
 			u = x
 			v = y
 			tr.InverseTransform(&u, &v)
-			dest.Set(int(x), int(y), compose(dest.At(int(x), int(y)), getColorLinear(src, u, v)))
+			c1 := dest.At(int(x), int(y))
+			var c2 image.Color
+			switch filter {
+			case LinearFilter:
+				c2 = getColorLinear(src, u, v)
+			case BilinearFilter:
+				c2 = getColorBilinear(src, u, v)
+			case BicubicFilter:
+				c2 = getColorBicubic(src, u, v)
+			}
+			var cr image.Color
+			switch op {
+			case draw.Over:
+				r1, g1, b1, a1 := c1.RGBA()
+				r2, g2, b2, a2 := c2.RGBA()
+				ia := M - a2
+				r := ((r1 * ia) / M) + r2
+				g := ((g1 * ia) / M) + g2
+				b := ((b1 * ia) / M) + b2
+				a := ((a1 * ia) / M) + a2
+				cr = image.RGBAColor{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
+			default:
+				cr = c2
+			}
+			dest.Set(int(x), int(y), cr)
 		}
 	}
 }

draw2d/transform.go

@@ -26,6 +26,23 @@ func (tr MatrixTransform) Transform(points ...*float64) {
 	}
 }
 
+func (tr MatrixTransform) TransformRectangle(x0, y0, x2, y2*float64) {
+	x1 := *x2
+	y1 := *y0
+	x3 := *x0
+	y3 := *y2
+	tr.Transform(x0, y0, &x1, &y1, x2, y2, &x3, &y3)
+	*x0, x1 = minMax(*x0, x1)
+	*x2, x3 = minMax(*x2, x3)
+	*y0, y1 = minMax(*y0, y1)
+	*y2, y3 = minMax(*y2, y3)
+
+	*x0 = min(*x0, *x2)
+	*y0 = min(*y0, *y2)
+	*x2 = max(x1, x3)
+	*y2 = max(y1, y3)
+}
+
 func (tr MatrixTransform) TransformRasterPoint(points ...*raster.Point) {
 	for _, point := range points {
 		x := float64(point.X) / 256