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draw.Draw fast paths for the Over operator.
Time (us) to draw a 200x200 src onto an image.RGBA dst with the Over operator. Each case was measured three separate times, and the sorted times are reported. Fill case (where src is an image.ColorImage): Before: 7438, 7511, 7526 After: 3073, 3087, 3102 Copy case (where src is an image.RGBA): Before: 9506, 9510, 9563 After: 5262, 5300, 5344 R=rsc CC=golang-dev https://golang.org/cl/1532041
This commit is contained in:
Nigel Tao
parent
c2e9f0c562
commit
2006667931
@ -12,6 +12,9 @@ package draw
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import "image"
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// m is the maximum color value returned by image.Color.RGBA.
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const m = 1<<16 - 1
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// A Porter-Duff compositing operator.
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type Op int
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@ -62,7 +65,20 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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// Fast paths for special cases. If none of them apply, then we fall back to a general but slow implementation.
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if dst0, ok := dst.(*image.RGBA); ok {
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if op == Over {
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if mask0, ok := mask.(*image.Alpha); ok {
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if mask == nil {
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if src0, ok := src.(image.ColorImage); ok {
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drawFillOver(dst0, r, src0)
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return
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}
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if src0, ok := src.(*image.RGBA); ok {
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if dst0 == src0 && r.Overlaps(r.Add(sp.Sub(r.Min))) {
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// TODO(nigeltao): Implement a fast path for the overlapping case.
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} else {
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drawCopyOver(dst0, r, src0, sp)
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return
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}
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}
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} else if mask0, ok := mask.(*image.Alpha); ok {
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if src0, ok := src.(image.ColorImage); ok {
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drawGlyphOver(dst0, r, src0, mask0, mp)
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return
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@ -71,14 +87,14 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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} else {
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if mask == nil {
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if src0, ok := src.(image.ColorImage); ok {
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drawFill(dst0, r, src0)
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drawFillSrc(dst0, r, src0)
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return
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}
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if src0, ok := src.(*image.RGBA); ok {
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if dst0 == src0 && r.Overlaps(r.Add(sp.Sub(r.Min))) {
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// TODO(nigeltao): Implement a fast path for the overlapping case.
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} else {
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drawCopy(dst0, r, src0, sp)
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drawCopySrc(dst0, r, src0, sp)
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return
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}
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}
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@ -105,8 +121,7 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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sx := sp.X + x0 - r.Min.X
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mx := mp.X + x0 - r.Min.X
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for x := x0; x != x1; x, sx, mx = x+dx, sx+dx, mx+dx {
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const M = 1<<16 - 1
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ma := uint32(M)
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ma := uint32(m)
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if mask != nil {
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_, _, _, ma = mask.At(mx, my).RGBA()
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}
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@ -117,7 +132,7 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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} else {
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dst.Set(x, y, zeroColor)
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}
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case ma == M && op == Src:
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case ma == m && op == Src:
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dst.Set(x, y, src.At(sx, sy))
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default:
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sr, sg, sb, sa := src.At(sx, sy).RGBA()
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@ -126,16 +141,16 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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}
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if op == Over {
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dr, dg, db, da := dst.At(x, y).RGBA()
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a := M - (sa * ma / M)
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out.R = uint16((dr*a + sr*ma) / M)
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out.G = uint16((dg*a + sg*ma) / M)
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out.B = uint16((db*a + sb*ma) / M)
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out.A = uint16((da*a + sa*ma) / M)
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a := m - (sa * ma / m)
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out.R = uint16((dr*a + sr*ma) / m)
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out.G = uint16((dg*a + sg*ma) / m)
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out.B = uint16((db*a + sb*ma) / m)
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out.A = uint16((da*a + sa*ma) / m)
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} else {
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out.R = uint16(sr * ma / M)
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out.G = uint16(sg * ma / M)
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out.B = uint16(sb * ma / M)
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out.A = uint16(sa * ma / M)
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out.R = uint16(sr * ma / m)
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out.G = uint16(sg * ma / m)
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out.B = uint16(sb * ma / m)
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out.A = uint16(sa * ma / m)
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}
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dst.Set(x, y, out)
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}
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@ -143,6 +158,52 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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}
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}
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func drawFillOver(dst *image.RGBA, r Rectangle, src image.ColorImage) {
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cr, cg, cb, ca := src.RGBA()
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// The 0x101 is here for the same reason as in drawRGBA.
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a := (m - ca) * 0x101
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x0, x1 := r.Min.X, r.Max.X
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y0, y1 := r.Min.Y, r.Max.Y
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for y := y0; y != y1; y++ {
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p := dst.Pixel[y]
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for x := x0; x != x1; x++ {
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rgba := p[x]
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dr := (uint32(rgba.R)*a)/m + cr
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dg := (uint32(rgba.G)*a)/m + cg
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db := (uint32(rgba.B)*a)/m + cb
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da := (uint32(rgba.A)*a)/m + ca
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p[x] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
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}
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}
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}
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func drawCopyOver(dst *image.RGBA, r Rectangle, src *image.RGBA, sp Point) {
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x0, x1 := r.Min.X, r.Max.X
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y0, y1 := r.Min.Y, r.Max.Y
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for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
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dpix := dst.Pixel[y]
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spix := src.Pixel[y]
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for x, sx := x0, sp.X; x != x1; x, sx = x+1, sx+1 {
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// For unknown reasons, even though both dpix[x] and spix[sx] are
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// image.RGBAColors, on an x86 CPU it seems fastest to call RGBA
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// for the source but to do it manually for the destination.
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sr, sg, sb, sa := spix[sx].RGBA()
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drgba := dpix[x]
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dr := uint32(drgba.R)
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dg := uint32(drgba.G)
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db := uint32(drgba.B)
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da := uint32(drgba.A)
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// The 0x101 is here for the same reason as in drawRGBA.
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a := (m - sa) * 0x101
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dr = (dr*a)/m + sr
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dg = (dg*a)/m + sg
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db = (db*a)/m + sb
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da = (da*a)/m + sa
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dpix[x] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
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}
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}
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}
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func drawGlyphOver(dst *image.RGBA, r Rectangle, src image.ColorImage, mask *image.Alpha, mp Point) {
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x0, x1 := r.Min.X, r.Max.X
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y0, y1 := r.Min.Y, r.Max.Y
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@ -160,19 +221,18 @@ func drawGlyphOver(dst *image.RGBA, r Rectangle, src image.ColorImage, mask *ima
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dg := uint32(rgba.G)
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db := uint32(rgba.B)
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da := uint32(rgba.A)
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const M = 1<<16 - 1
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// The 0x101 is here for the same reason as in drawRGBA.
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a := (M - (ca * ma / M)) * 0x101
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dr = (dr*a + cr*ma) / M
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dg = (dg*a + cg*ma) / M
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db = (db*a + cb*ma) / M
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da = (da*a + ca*ma) / M
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a := (m - (ca * ma / m)) * 0x101
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dr = (dr*a + cr*ma) / m
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dg = (dg*a + cg*ma) / m
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db = (db*a + cb*ma) / m
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da = (da*a + ca*ma) / m
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p[x] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
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}
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}
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}
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func drawFill(dst *image.RGBA, r Rectangle, src image.ColorImage) {
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func drawFillSrc(dst *image.RGBA, r Rectangle, src image.ColorImage) {
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if r.Dy() < 1 {
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return
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}
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@ -193,7 +253,7 @@ func drawFill(dst *image.RGBA, r Rectangle, src image.ColorImage) {
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}
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}
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func drawCopy(dst *image.RGBA, r Rectangle, src *image.RGBA, sp Point) {
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func drawCopySrc(dst *image.RGBA, r Rectangle, src *image.RGBA, sp Point) {
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dx0, dx1 := r.Min.X, r.Max.X
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dy0, dy1 := r.Min.Y, r.Max.Y
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sx0, sx1 := sp.X, sp.X+dx1-dx0
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@ -219,8 +279,7 @@ func drawRGBA(dst *image.RGBA, r Rectangle, src image.Image, sp Point, mask imag
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mx := mp.X + x0 - r.Min.X
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p := dst.Pixel[y]
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for x := x0; x != x1; x, sx, mx = x+dx, sx+dx, mx+dx {
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const M = 1<<16 - 1
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ma := uint32(M)
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ma := uint32(m)
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if mask != nil {
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_, _, _, ma = mask.At(mx, my).RGBA()
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}
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@ -238,16 +297,16 @@ func drawRGBA(dst *image.RGBA, r Rectangle, src image.Image, sp Point, mask imag
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// and similarly for dg, db and da, but instead we multiply a
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// (which is a 16-bit color, ranging in [0,65535]) by 0x101.
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// This yields the same result, but is fewer arithmetic operations.
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a := (M - (sa * ma / M)) * 0x101
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dr = (dr*a + sr*ma) / M
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dg = (dg*a + sg*ma) / M
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db = (db*a + sb*ma) / M
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da = (da*a + sa*ma) / M
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a := (m - (sa * ma / m)) * 0x101
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dr = (dr*a + sr*ma) / m
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dg = (dg*a + sg*ma) / m
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db = (db*a + sb*ma) / m
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da = (da*a + sa*ma) / m
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} else {
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dr = sr * ma / M
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dg = sg * ma / M
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db = sb * ma / M
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da = sa * ma / M
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dr = sr * ma / m
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dg = sg * ma / m
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db = sb * ma / m
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da = sa * ma / m
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}
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p[x] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
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}
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