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path: root/src/pkg/image/draw/draw.go
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Diffstat (limited to 'src/pkg/image/draw/draw.go')
-rw-r--r--src/pkg/image/draw/draw.go673
1 files changed, 0 insertions, 673 deletions
diff --git a/src/pkg/image/draw/draw.go b/src/pkg/image/draw/draw.go
deleted file mode 100644
index 661230e7c..000000000
--- a/src/pkg/image/draw/draw.go
+++ /dev/null
@@ -1,673 +0,0 @@
-// Copyright 2009 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package draw provides image composition functions.
-//
-// See "The Go image/draw package" for an introduction to this package:
-// http://golang.org/doc/articles/image_draw.html
-package draw
-
-import (
- "image"
- "image/color"
-)
-
-// m is the maximum color value returned by image.Color.RGBA.
-const m = 1<<16 - 1
-
-// Image is an image.Image with a Set method to change a single pixel.
-type Image interface {
- image.Image
- Set(x, y int, c color.Color)
-}
-
-// Quantizer produces a palette for an image.
-type Quantizer interface {
- // Quantize appends up to cap(p) - len(p) colors to p and returns the
- // updated palette suitable for converting m to a paletted image.
- Quantize(p color.Palette, m image.Image) color.Palette
-}
-
-// Op is a Porter-Duff compositing operator.
-type Op int
-
-const (
- // Over specifies ``(src in mask) over dst''.
- Over Op = iota
- // Src specifies ``src in mask''.
- Src
-)
-
-// Draw implements the Drawer interface by calling the Draw function with this
-// Op.
-func (op Op) Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point) {
- DrawMask(dst, r, src, sp, nil, image.Point{}, op)
-}
-
-// Drawer contains the Draw method.
-type Drawer interface {
- // Draw aligns r.Min in dst with sp in src and then replaces the
- // rectangle r in dst with the result of drawing src on dst.
- Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point)
-}
-
-// FloydSteinberg is a Drawer that is the Src Op with Floyd-Steinberg error
-// diffusion.
-var FloydSteinberg Drawer = floydSteinberg{}
-
-type floydSteinberg struct{}
-
-func (floydSteinberg) Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point) {
- clip(dst, &r, src, &sp, nil, nil)
- if r.Empty() {
- return
- }
- drawPaletted(dst, r, src, sp, true)
-}
-
-// clip clips r against each image's bounds (after translating into the
-// destination image's co-ordinate space) and shifts the points sp and mp by
-// the same amount as the change in r.Min.
-func clip(dst Image, r *image.Rectangle, src image.Image, sp *image.Point, mask image.Image, mp *image.Point) {
- orig := r.Min
- *r = r.Intersect(dst.Bounds())
- *r = r.Intersect(src.Bounds().Add(orig.Sub(*sp)))
- if mask != nil {
- *r = r.Intersect(mask.Bounds().Add(orig.Sub(*mp)))
- }
- dx := r.Min.X - orig.X
- dy := r.Min.Y - orig.Y
- if dx == 0 && dy == 0 {
- return
- }
- (*sp).X += dx
- (*sp).Y += dy
- (*mp).X += dx
- (*mp).Y += dy
-}
-
-func processBackward(dst Image, r image.Rectangle, src image.Image, sp image.Point) bool {
- return image.Image(dst) == src &&
- r.Overlaps(r.Add(sp.Sub(r.Min))) &&
- (sp.Y < r.Min.Y || (sp.Y == r.Min.Y && sp.X < r.Min.X))
-}
-
-// Draw calls DrawMask with a nil mask.
-func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op) {
- DrawMask(dst, r, src, sp, nil, image.Point{}, op)
-}
-
-// DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r
-// in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque.
-func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op) {
- clip(dst, &r, src, &sp, mask, &mp)
- if r.Empty() {
- return
- }
-
- // Fast paths for special cases. If none of them apply, then we fall back to a general but slow implementation.
- switch dst0 := dst.(type) {
- case *image.RGBA:
- if op == Over {
- if mask == nil {
- switch src0 := src.(type) {
- case *image.Uniform:
- drawFillOver(dst0, r, src0)
- return
- case *image.RGBA:
- drawCopyOver(dst0, r, src0, sp)
- return
- case *image.NRGBA:
- drawNRGBAOver(dst0, r, src0, sp)
- return
- case *image.YCbCr:
- if drawYCbCr(dst0, r, src0, sp) {
- return
- }
- }
- } else if mask0, ok := mask.(*image.Alpha); ok {
- switch src0 := src.(type) {
- case *image.Uniform:
- drawGlyphOver(dst0, r, src0, mask0, mp)
- return
- }
- }
- } else {
- if mask == nil {
- switch src0 := src.(type) {
- case *image.Uniform:
- drawFillSrc(dst0, r, src0)
- return
- case *image.RGBA:
- drawCopySrc(dst0, r, src0, sp)
- return
- case *image.NRGBA:
- drawNRGBASrc(dst0, r, src0, sp)
- return
- case *image.YCbCr:
- if drawYCbCr(dst0, r, src0, sp) {
- return
- }
- }
- }
- }
- drawRGBA(dst0, r, src, sp, mask, mp, op)
- return
- case *image.Paletted:
- if op == Src && mask == nil && !processBackward(dst, r, src, sp) {
- drawPaletted(dst0, r, src, sp, false)
- }
- }
-
- x0, x1, dx := r.Min.X, r.Max.X, 1
- y0, y1, dy := r.Min.Y, r.Max.Y, 1
- if processBackward(dst, r, src, sp) {
- x0, x1, dx = x1-1, x0-1, -1
- y0, y1, dy = y1-1, y0-1, -1
- }
-
- var out color.RGBA64
- sy := sp.Y + y0 - r.Min.Y
- my := mp.Y + y0 - r.Min.Y
- for y := y0; y != y1; y, sy, my = y+dy, sy+dy, my+dy {
- sx := sp.X + x0 - r.Min.X
- mx := mp.X + x0 - r.Min.X
- for x := x0; x != x1; x, sx, mx = x+dx, sx+dx, mx+dx {
- ma := uint32(m)
- if mask != nil {
- _, _, _, ma = mask.At(mx, my).RGBA()
- }
- switch {
- case ma == 0:
- if op == Over {
- // No-op.
- } else {
- dst.Set(x, y, color.Transparent)
- }
- case ma == m && op == Src:
- dst.Set(x, y, src.At(sx, sy))
- default:
- sr, sg, sb, sa := src.At(sx, sy).RGBA()
- if op == Over {
- dr, dg, db, da := dst.At(x, y).RGBA()
- a := m - (sa * ma / m)
- out.R = uint16((dr*a + sr*ma) / m)
- out.G = uint16((dg*a + sg*ma) / m)
- out.B = uint16((db*a + sb*ma) / m)
- out.A = uint16((da*a + sa*ma) / m)
- } else {
- out.R = uint16(sr * ma / m)
- out.G = uint16(sg * ma / m)
- out.B = uint16(sb * ma / m)
- out.A = uint16(sa * ma / m)
- }
- // The third argument is &out instead of out (and out is
- // declared outside of the inner loop) to avoid the implicit
- // conversion to color.Color here allocating memory in the
- // inner loop if sizeof(color.RGBA64) > sizeof(uintptr).
- dst.Set(x, y, &out)
- }
- }
- }
-}
-
-func drawFillOver(dst *image.RGBA, r image.Rectangle, src *image.Uniform) {
- sr, sg, sb, sa := src.RGBA()
- // The 0x101 is here for the same reason as in drawRGBA.
- a := (m - sa) * 0x101
- i0 := dst.PixOffset(r.Min.X, r.Min.Y)
- i1 := i0 + r.Dx()*4
- for y := r.Min.Y; y != r.Max.Y; y++ {
- for i := i0; i < i1; i += 4 {
- dr := uint32(dst.Pix[i+0])
- dg := uint32(dst.Pix[i+1])
- db := uint32(dst.Pix[i+2])
- da := uint32(dst.Pix[i+3])
-
- dst.Pix[i+0] = uint8((dr*a/m + sr) >> 8)
- dst.Pix[i+1] = uint8((dg*a/m + sg) >> 8)
- dst.Pix[i+2] = uint8((db*a/m + sb) >> 8)
- dst.Pix[i+3] = uint8((da*a/m + sa) >> 8)
- }
- i0 += dst.Stride
- i1 += dst.Stride
- }
-}
-
-func drawFillSrc(dst *image.RGBA, r image.Rectangle, src *image.Uniform) {
- sr, sg, sb, sa := src.RGBA()
- // The built-in copy function is faster than a straightforward for loop to fill the destination with
- // the color, but copy requires a slice source. We therefore use a for loop to fill the first row, and
- // then use the first row as the slice source for the remaining rows.
- i0 := dst.PixOffset(r.Min.X, r.Min.Y)
- i1 := i0 + r.Dx()*4
- for i := i0; i < i1; i += 4 {
- dst.Pix[i+0] = uint8(sr >> 8)
- dst.Pix[i+1] = uint8(sg >> 8)
- dst.Pix[i+2] = uint8(sb >> 8)
- dst.Pix[i+3] = uint8(sa >> 8)
- }
- firstRow := dst.Pix[i0:i1]
- for y := r.Min.Y + 1; y < r.Max.Y; y++ {
- i0 += dst.Stride
- i1 += dst.Stride
- copy(dst.Pix[i0:i1], firstRow)
- }
-}
-
-func drawCopyOver(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.Point) {
- dx, dy := r.Dx(), r.Dy()
- d0 := dst.PixOffset(r.Min.X, r.Min.Y)
- s0 := src.PixOffset(sp.X, sp.Y)
- var (
- ddelta, sdelta int
- i0, i1, idelta int
- )
- if r.Min.Y < sp.Y || r.Min.Y == sp.Y && r.Min.X <= sp.X {
- ddelta = dst.Stride
- sdelta = src.Stride
- i0, i1, idelta = 0, dx*4, +4
- } else {
- // If the source start point is higher than the destination start point, or equal height but to the left,
- // then we compose the rows in right-to-left, bottom-up order instead of left-to-right, top-down.
- d0 += (dy - 1) * dst.Stride
- s0 += (dy - 1) * src.Stride
- ddelta = -dst.Stride
- sdelta = -src.Stride
- i0, i1, idelta = (dx-1)*4, -4, -4
- }
- for ; dy > 0; dy-- {
- dpix := dst.Pix[d0:]
- spix := src.Pix[s0:]
- for i := i0; i != i1; i += idelta {
- sr := uint32(spix[i+0]) * 0x101
- sg := uint32(spix[i+1]) * 0x101
- sb := uint32(spix[i+2]) * 0x101
- sa := uint32(spix[i+3]) * 0x101
-
- dr := uint32(dpix[i+0])
- dg := uint32(dpix[i+1])
- db := uint32(dpix[i+2])
- da := uint32(dpix[i+3])
-
- // The 0x101 is here for the same reason as in drawRGBA.
- a := (m - sa) * 0x101
-
- dpix[i+0] = uint8((dr*a/m + sr) >> 8)
- dpix[i+1] = uint8((dg*a/m + sg) >> 8)
- dpix[i+2] = uint8((db*a/m + sb) >> 8)
- dpix[i+3] = uint8((da*a/m + sa) >> 8)
- }
- d0 += ddelta
- s0 += sdelta
- }
-}
-
-func drawCopySrc(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.Point) {
- n, dy := 4*r.Dx(), r.Dy()
- d0 := dst.PixOffset(r.Min.X, r.Min.Y)
- s0 := src.PixOffset(sp.X, sp.Y)
- var ddelta, sdelta int
- if r.Min.Y <= sp.Y {
- ddelta = dst.Stride
- sdelta = src.Stride
- } else {
- // If the source start point is higher than the destination start point, then we compose the rows
- // in bottom-up order instead of top-down. Unlike the drawCopyOver function, we don't have to
- // check the x co-ordinates because the built-in copy function can handle overlapping slices.
- d0 += (dy - 1) * dst.Stride
- s0 += (dy - 1) * src.Stride
- ddelta = -dst.Stride
- sdelta = -src.Stride
- }
- for ; dy > 0; dy-- {
- copy(dst.Pix[d0:d0+n], src.Pix[s0:s0+n])
- d0 += ddelta
- s0 += sdelta
- }
-}
-
-func drawNRGBAOver(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image.Point) {
- i0 := (r.Min.X - dst.Rect.Min.X) * 4
- i1 := (r.Max.X - dst.Rect.Min.X) * 4
- si0 := (sp.X - src.Rect.Min.X) * 4
- yMax := r.Max.Y - dst.Rect.Min.Y
-
- y := r.Min.Y - dst.Rect.Min.Y
- sy := sp.Y - src.Rect.Min.Y
- for ; y != yMax; y, sy = y+1, sy+1 {
- dpix := dst.Pix[y*dst.Stride:]
- spix := src.Pix[sy*src.Stride:]
-
- for i, si := i0, si0; i < i1; i, si = i+4, si+4 {
- // Convert from non-premultiplied color to pre-multiplied color.
- sa := uint32(spix[si+3]) * 0x101
- sr := uint32(spix[si+0]) * sa / 0xff
- sg := uint32(spix[si+1]) * sa / 0xff
- sb := uint32(spix[si+2]) * sa / 0xff
-
- dr := uint32(dpix[i+0])
- dg := uint32(dpix[i+1])
- db := uint32(dpix[i+2])
- da := uint32(dpix[i+3])
-
- // The 0x101 is here for the same reason as in drawRGBA.
- a := (m - sa) * 0x101
-
- dpix[i+0] = uint8((dr*a/m + sr) >> 8)
- dpix[i+1] = uint8((dg*a/m + sg) >> 8)
- dpix[i+2] = uint8((db*a/m + sb) >> 8)
- dpix[i+3] = uint8((da*a/m + sa) >> 8)
- }
- }
-}
-
-func drawNRGBASrc(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image.Point) {
- i0 := (r.Min.X - dst.Rect.Min.X) * 4
- i1 := (r.Max.X - dst.Rect.Min.X) * 4
- si0 := (sp.X - src.Rect.Min.X) * 4
- yMax := r.Max.Y - dst.Rect.Min.Y
-
- y := r.Min.Y - dst.Rect.Min.Y
- sy := sp.Y - src.Rect.Min.Y
- for ; y != yMax; y, sy = y+1, sy+1 {
- dpix := dst.Pix[y*dst.Stride:]
- spix := src.Pix[sy*src.Stride:]
-
- for i, si := i0, si0; i < i1; i, si = i+4, si+4 {
- // Convert from non-premultiplied color to pre-multiplied color.
- sa := uint32(spix[si+3]) * 0x101
- sr := uint32(spix[si+0]) * sa / 0xff
- sg := uint32(spix[si+1]) * sa / 0xff
- sb := uint32(spix[si+2]) * sa / 0xff
-
- dpix[i+0] = uint8(sr >> 8)
- dpix[i+1] = uint8(sg >> 8)
- dpix[i+2] = uint8(sb >> 8)
- dpix[i+3] = uint8(sa >> 8)
- }
- }
-}
-
-func drawYCbCr(dst *image.RGBA, r image.Rectangle, src *image.YCbCr, sp image.Point) (ok bool) {
- // An image.YCbCr is always fully opaque, and so if the mask is implicitly nil
- // (i.e. fully opaque) then the op is effectively always Src.
- x0 := (r.Min.X - dst.Rect.Min.X) * 4
- x1 := (r.Max.X - dst.Rect.Min.X) * 4
- y0 := r.Min.Y - dst.Rect.Min.Y
- y1 := r.Max.Y - dst.Rect.Min.Y
- switch src.SubsampleRatio {
- case image.YCbCrSubsampleRatio444:
- for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
- dpix := dst.Pix[y*dst.Stride:]
- yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
- ci := (sy-src.Rect.Min.Y)*src.CStride + (sp.X - src.Rect.Min.X)
- for x := x0; x != x1; x, yi, ci = x+4, yi+1, ci+1 {
- rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
- dpix[x+0] = rr
- dpix[x+1] = gg
- dpix[x+2] = bb
- dpix[x+3] = 255
- }
- }
- case image.YCbCrSubsampleRatio422:
- for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
- dpix := dst.Pix[y*dst.Stride:]
- yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
- ciBase := (sy-src.Rect.Min.Y)*src.CStride - src.Rect.Min.X/2
- for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {
- ci := ciBase + sx/2
- rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
- dpix[x+0] = rr
- dpix[x+1] = gg
- dpix[x+2] = bb
- dpix[x+3] = 255
- }
- }
- case image.YCbCrSubsampleRatio420:
- for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
- dpix := dst.Pix[y*dst.Stride:]
- yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
- ciBase := (sy/2-src.Rect.Min.Y/2)*src.CStride - src.Rect.Min.X/2
- for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {
- ci := ciBase + sx/2
- rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
- dpix[x+0] = rr
- dpix[x+1] = gg
- dpix[x+2] = bb
- dpix[x+3] = 255
- }
- }
- case image.YCbCrSubsampleRatio440:
- for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
- dpix := dst.Pix[y*dst.Stride:]
- yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)
- ci := (sy/2-src.Rect.Min.Y/2)*src.CStride + (sp.X - src.Rect.Min.X)
- for x := x0; x != x1; x, yi, ci = x+4, yi+1, ci+1 {
- rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])
- dpix[x+0] = rr
- dpix[x+1] = gg
- dpix[x+2] = bb
- dpix[x+3] = 255
- }
- }
- default:
- return false
- }
- return true
-}
-
-func drawGlyphOver(dst *image.RGBA, r image.Rectangle, src *image.Uniform, mask *image.Alpha, mp image.Point) {
- i0 := dst.PixOffset(r.Min.X, r.Min.Y)
- i1 := i0 + r.Dx()*4
- mi0 := mask.PixOffset(mp.X, mp.Y)
- sr, sg, sb, sa := src.RGBA()
- for y, my := r.Min.Y, mp.Y; y != r.Max.Y; y, my = y+1, my+1 {
- for i, mi := i0, mi0; i < i1; i, mi = i+4, mi+1 {
- ma := uint32(mask.Pix[mi])
- if ma == 0 {
- continue
- }
- ma |= ma << 8
-
- dr := uint32(dst.Pix[i+0])
- dg := uint32(dst.Pix[i+1])
- db := uint32(dst.Pix[i+2])
- da := uint32(dst.Pix[i+3])
-
- // The 0x101 is here for the same reason as in drawRGBA.
- a := (m - (sa * ma / m)) * 0x101
-
- dst.Pix[i+0] = uint8((dr*a + sr*ma) / m >> 8)
- dst.Pix[i+1] = uint8((dg*a + sg*ma) / m >> 8)
- dst.Pix[i+2] = uint8((db*a + sb*ma) / m >> 8)
- dst.Pix[i+3] = uint8((da*a + sa*ma) / m >> 8)
- }
- i0 += dst.Stride
- i1 += dst.Stride
- mi0 += mask.Stride
- }
-}
-
-func drawRGBA(dst *image.RGBA, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op) {
- x0, x1, dx := r.Min.X, r.Max.X, 1
- y0, y1, dy := r.Min.Y, r.Max.Y, 1
- if image.Image(dst) == src && r.Overlaps(r.Add(sp.Sub(r.Min))) {
- if sp.Y < r.Min.Y || sp.Y == r.Min.Y && sp.X < r.Min.X {
- x0, x1, dx = x1-1, x0-1, -1
- y0, y1, dy = y1-1, y0-1, -1
- }
- }
-
- sy := sp.Y + y0 - r.Min.Y
- my := mp.Y + y0 - r.Min.Y
- sx0 := sp.X + x0 - r.Min.X
- mx0 := mp.X + x0 - r.Min.X
- sx1 := sx0 + (x1 - x0)
- i0 := dst.PixOffset(x0, y0)
- di := dx * 4
- for y := y0; y != y1; y, sy, my = y+dy, sy+dy, my+dy {
- for i, sx, mx := i0, sx0, mx0; sx != sx1; i, sx, mx = i+di, sx+dx, mx+dx {
- ma := uint32(m)
- if mask != nil {
- _, _, _, ma = mask.At(mx, my).RGBA()
- }
- sr, sg, sb, sa := src.At(sx, sy).RGBA()
- if op == Over {
- dr := uint32(dst.Pix[i+0])
- dg := uint32(dst.Pix[i+1])
- db := uint32(dst.Pix[i+2])
- da := uint32(dst.Pix[i+3])
-
- // dr, dg, db and da are all 8-bit color at the moment, ranging in [0,255].
- // We work in 16-bit color, and so would normally do:
- // dr |= dr << 8
- // and similarly for dg, db and da, but instead we multiply a
- // (which is a 16-bit color, ranging in [0,65535]) by 0x101.
- // This yields the same result, but is fewer arithmetic operations.
- a := (m - (sa * ma / m)) * 0x101
-
- dst.Pix[i+0] = uint8((dr*a + sr*ma) / m >> 8)
- dst.Pix[i+1] = uint8((dg*a + sg*ma) / m >> 8)
- dst.Pix[i+2] = uint8((db*a + sb*ma) / m >> 8)
- dst.Pix[i+3] = uint8((da*a + sa*ma) / m >> 8)
-
- } else {
- dst.Pix[i+0] = uint8(sr * ma / m >> 8)
- dst.Pix[i+1] = uint8(sg * ma / m >> 8)
- dst.Pix[i+2] = uint8(sb * ma / m >> 8)
- dst.Pix[i+3] = uint8(sa * ma / m >> 8)
- }
- }
- i0 += dy * dst.Stride
- }
-}
-
-// clamp clamps i to the interval [0, 0xffff].
-func clamp(i int32) int32 {
- if i < 0 {
- return 0
- }
- if i > 0xffff {
- return 0xffff
- }
- return i
-}
-
-func drawPaletted(dst Image, r image.Rectangle, src image.Image, sp image.Point, floydSteinberg bool) {
- // TODO(nigeltao): handle the case where the dst and src overlap.
- // Does it even make sense to try and do Floyd-Steinberg whilst
- // walking the image backward (right-to-left bottom-to-top)?
-
- // If dst is an *image.Paletted, we have a fast path for dst.Set and
- // dst.At. The dst.Set equivalent is a batch version of the algorithm
- // used by color.Palette's Index method in image/color/color.go, plus
- // optional Floyd-Steinberg error diffusion.
- palette, pix, stride := [][3]int32(nil), []byte(nil), 0
- if p, ok := dst.(*image.Paletted); ok {
- palette = make([][3]int32, len(p.Palette))
- for i, col := range p.Palette {
- r, g, b, _ := col.RGBA()
- palette[i][0] = int32(r)
- palette[i][1] = int32(g)
- palette[i][2] = int32(b)
- }
- pix, stride = p.Pix[p.PixOffset(r.Min.X, r.Min.Y):], p.Stride
- }
-
- // quantErrorCurr and quantErrorNext are the Floyd-Steinberg quantization
- // errors that have been propagated to the pixels in the current and next
- // rows. The +2 simplifies calculation near the edges.
- var quantErrorCurr, quantErrorNext [][3]int32
- if floydSteinberg {
- quantErrorCurr = make([][3]int32, r.Dx()+2)
- quantErrorNext = make([][3]int32, r.Dx()+2)
- }
-
- // Loop over each source pixel.
- out := color.RGBA64{A: 0xffff}
- for y := 0; y != r.Dy(); y++ {
- for x := 0; x != r.Dx(); x++ {
- // er, eg and eb are the pixel's R,G,B values plus the
- // optional Floyd-Steinberg error.
- sr, sg, sb, _ := src.At(sp.X+x, sp.Y+y).RGBA()
- er, eg, eb := int32(sr), int32(sg), int32(sb)
- if floydSteinberg {
- er = clamp(er + quantErrorCurr[x+1][0]/16)
- eg = clamp(eg + quantErrorCurr[x+1][1]/16)
- eb = clamp(eb + quantErrorCurr[x+1][2]/16)
- }
-
- if palette != nil {
- // Find the closest palette color in Euclidean R,G,B space: the
- // one that minimizes sum-squared-difference. We shift by 1 bit
- // to avoid potential uint32 overflow in sum-squared-difference.
- // TODO(nigeltao): consider smarter algorithms.
- bestIndex, bestSSD := 0, uint32(1<<32-1)
- for index, p := range palette {
- delta := (er - p[0]) >> 1
- ssd := uint32(delta * delta)
- delta = (eg - p[1]) >> 1
- ssd += uint32(delta * delta)
- delta = (eb - p[2]) >> 1
- ssd += uint32(delta * delta)
- if ssd < bestSSD {
- bestIndex, bestSSD = index, ssd
- if ssd == 0 {
- break
- }
- }
- }
- pix[y*stride+x] = byte(bestIndex)
-
- if !floydSteinberg {
- continue
- }
- er -= int32(palette[bestIndex][0])
- eg -= int32(palette[bestIndex][1])
- eb -= int32(palette[bestIndex][2])
-
- } else {
- out.R = uint16(er)
- out.G = uint16(eg)
- out.B = uint16(eb)
- // The third argument is &out instead of out (and out is
- // declared outside of the inner loop) to avoid the implicit
- // conversion to color.Color here allocating memory in the
- // inner loop if sizeof(color.RGBA64) > sizeof(uintptr).
- dst.Set(r.Min.X+x, r.Min.Y+y, &out)
-
- if !floydSteinberg {
- continue
- }
- sr, sg, sb, _ = dst.At(r.Min.X+x, r.Min.Y+y).RGBA()
- er -= int32(sr)
- eg -= int32(sg)
- eb -= int32(sb)
- }
-
- // Propagate the Floyd-Steinberg quantization error.
- quantErrorNext[x+0][0] += er * 3
- quantErrorNext[x+0][1] += eg * 3
- quantErrorNext[x+0][2] += eb * 3
- quantErrorNext[x+1][0] += er * 5
- quantErrorNext[x+1][1] += eg * 5
- quantErrorNext[x+1][2] += eb * 5
- quantErrorNext[x+2][0] += er * 1
- quantErrorNext[x+2][1] += eg * 1
- quantErrorNext[x+2][2] += eb * 1
- quantErrorCurr[x+2][0] += er * 7
- quantErrorCurr[x+2][1] += eg * 7
- quantErrorCurr[x+2][2] += eb * 7
- }
-
- // Recycle the quantization error buffers.
- if floydSteinberg {
- quantErrorCurr, quantErrorNext = quantErrorNext, quantErrorCurr
- for i := range quantErrorNext {
- quantErrorNext[i] = [3]int32{}
- }
- }
- }
-}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-25 06:35:09 +0000