// 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: // https://golang.org/doc/articles/image_draw.html package draw import ( "image" "image/color" "image/internal/imageutil" ) // 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) } // RGBA64Image extends both the [Image] and [image.RGBA64Image] interfaces with a // SetRGBA64 method to change a single pixel. SetRGBA64 is equivalent to // calling Set, but it can avoid allocations from converting concrete color // types to the [color.Color] interface type. type RGBA64Image interface { image.RGBA64Image Set(x, y int, c color.Color) SetRGBA64(x, y int, c color.RGBA64) } // 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 coordinate 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 if mp != nil { mp.X += dx mp.Y += dy } } func processBackward(dst image.Image, r image.Rectangle, src image.Image, sp image.Point) bool { return 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 general but slower implementations. // // For NRGBA and NRGBA64 image types, the code paths aren't just faster. // They also avoid the information loss that would otherwise occur from // converting non-alpha-premultiplied color to and from alpha-premultiplied // color. See TestDrawSrcNonpremultiplied. switch dst0 := dst.(type) { case *image.RGBA: if op == Over { if mask == nil { switch src0 := src.(type) { case *image.Uniform: sr, sg, sb, sa := src0.RGBA() if sa == 0xffff { drawFillSrc(dst0, r, sr, sg, sb, sa) } else { drawFillOver(dst0, r, sr, sg, sb, sa) } return case *image.RGBA: drawCopyOver(dst0, r, src0, sp) return case *image.NRGBA: drawNRGBAOver(dst0, r, src0, sp) return case *image.YCbCr: // An image.YCbCr is always fully opaque, and so if the // mask is nil (i.e. fully opaque) then the op is // effectively always Src. Similarly for image.Gray and // image.CMYK. if imageutil.DrawYCbCr(dst0, r, src0, sp) { return } case *image.Gray: drawGray(dst0, r, src0, sp) return case *image.CMYK: drawCMYK(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 case *image.RGBA: drawRGBAMaskOver(dst0, r, src0, sp, mask0, mp) return case *image.Gray: drawGrayMaskOver(dst0, r, src0, sp, mask0, mp) return // Case order matters. The next case (image.RGBA64Image) is an // interface type that the concrete types above also implement. case image.RGBA64Image: drawRGBA64ImageMaskOver(dst0, r, src0, sp, mask0, mp) return } } } else { if mask == nil { switch src0 := src.(type) { case *image.Uniform: sr, sg, sb, sa := src0.RGBA() drawFillSrc(dst0, r, sr, sg, sb, sa) return case *image.RGBA: d0 := dst0.PixOffset(r.Min.X, r.Min.Y) s0 := src0.PixOffset(sp.X, sp.Y) drawCopySrc( dst0.Pix[d0:], dst0.Stride, r, src0.Pix[s0:], src0.Stride, sp, 4*r.Dx()) return case *image.NRGBA: drawNRGBASrc(dst0, r, src0, sp) return case *image.YCbCr: if imageutil.DrawYCbCr(dst0, r, src0, sp) { return } case *image.Gray: drawGray(dst0, r, src0, sp) return case *image.CMYK: drawCMYK(dst0, r, src0, sp) return } } } drawRGBA(dst0, r, src, sp, mask, mp, op) return case *image.Paletted: if op == Src && mask == nil { if src0, ok := src.(*image.Uniform); ok { colorIndex := uint8(dst0.Palette.Index(src0.C)) i0 := dst0.PixOffset(r.Min.X, r.Min.Y) i1 := i0 + r.Dx() for i := i0; i < i1; i++ { dst0.Pix[i] = colorIndex } firstRow := dst0.Pix[i0:i1] for y := r.Min.Y + 1; y < r.Max.Y; y++ { i0 += dst0.Stride i1 += dst0.Stride copy(dst0.Pix[i0:i1], firstRow) } return } else if !processBackward(dst, r, src, sp) { drawPaletted(dst0, r, src, sp, false) return } } case *image.NRGBA: if op == Src && mask == nil { if src0, ok := src.(*image.NRGBA); ok { d0 := dst0.PixOffset(r.Min.X, r.Min.Y) s0 := src0.PixOffset(sp.X, sp.Y) drawCopySrc( dst0.Pix[d0:], dst0.Stride, r, src0.Pix[s0:], src0.Stride, sp, 4*r.Dx()) return } } case *image.NRGBA64: if op == Src && mask == nil { if src0, ok := src.(*image.NRGBA64); ok { d0 := dst0.PixOffset(r.Min.X, r.Min.Y) s0 := src0.PixOffset(sp.X, sp.Y) drawCopySrc( dst0.Pix[d0:], dst0.Stride, r, src0.Pix[s0:], src0.Stride, sp, 8*r.Dx()) return } } } 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 } // FALLBACK1.17 // // Try the draw.RGBA64Image and image.RGBA64Image interfaces, part of the // standard library since Go 1.17. These are like the draw.Image and // image.Image interfaces but they can avoid allocations from converting // concrete color types to the color.Color interface type. if dst0, _ := dst.(RGBA64Image); dst0 != nil { if src0, _ := src.(image.RGBA64Image); src0 != nil { if mask == nil { 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 { if op == Src { dst0.SetRGBA64(x, y, src0.RGBA64At(sx, sy)) } else { srgba := src0.RGBA64At(sx, sy) a := m - uint32(srgba.A) drgba := dst0.RGBA64At(x, y) dst0.SetRGBA64(x, y, color.RGBA64{ R: uint16((uint32(drgba.R)*a)/m) + srgba.R, G: uint16((uint32(drgba.G)*a)/m) + srgba.G, B: uint16((uint32(drgba.B)*a)/m) + srgba.B, A: uint16((uint32(drgba.A)*a)/m) + srgba.A, }) } } } return } else if mask0, _ := mask.(image.RGBA64Image); mask0 != nil { 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(mask0.RGBA64At(mx, my).A) switch { case ma == 0: if op == Over { // No-op. } else { dst0.SetRGBA64(x, y, color.RGBA64{}) } case ma == m && op == Src: dst0.SetRGBA64(x, y, src0.RGBA64At(sx, sy)) default: srgba := src0.RGBA64At(sx, sy) if op == Over { drgba := dst0.RGBA64At(x, y) a := m - (uint32(srgba.A) * ma / m) dst0.SetRGBA64(x, y, color.RGBA64{ R: uint16((uint32(drgba.R)*a + uint32(srgba.R)*ma) / m), G: uint16((uint32(drgba.G)*a + uint32(srgba.G)*ma) / m), B: uint16((uint32(drgba.B)*a + uint32(srgba.B)*ma) / m), A: uint16((uint32(drgba.A)*a + uint32(srgba.A)*ma) / m), }) } else { dst0.SetRGBA64(x, y, color.RGBA64{ R: uint16(uint32(srgba.R) * ma / m), G: uint16(uint32(srgba.G) * ma / m), B: uint16(uint32(srgba.B) * ma / m), A: uint16(uint32(srgba.A) * ma / m), }) } } } } return } } } // FALLBACK1.0 // // If none of the faster code paths above apply, use the draw.Image and // image.Image interfaces, part of the standard library since Go 1.0. 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, sr, sg, sb, sa uint32) { // 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 := &dst.Pix[i+0] dg := &dst.Pix[i+1] db := &dst.Pix[i+2] da := &dst.Pix[i+3] *dr = uint8((uint32(*dr)*a/m + sr) >> 8) *dg = uint8((uint32(*dg)*a/m + sg) >> 8) *db = uint8((uint32(*db)*a/m + sb) >> 8) *da = uint8((uint32(*da)*a/m + sa) >> 8) } i0 += dst.Stride i1 += dst.Stride } } func drawFillSrc(dst *image.RGBA, r image.Rectangle, sr, sg, sb, sa uint32) { sr8 := uint8(sr >> 8) sg8 := uint8(sg >> 8) sb8 := uint8(sb >> 8) sa8 := uint8(sa >> 8) // 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] = sr8 dst.Pix[i+1] = sg8 dst.Pix[i+2] = sb8 dst.Pix[i+3] = sa8 } 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 { s := spix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 sr := uint32(s[0]) * 0x101 sg := uint32(s[1]) * 0x101 sb := uint32(s[2]) * 0x101 sa := uint32(s[3]) * 0x101 // The 0x101 is here for the same reason as in drawRGBA. a := (m - sa) * 0x101 d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 d[0] = uint8((uint32(d[0])*a/m + sr) >> 8) d[1] = uint8((uint32(d[1])*a/m + sg) >> 8) d[2] = uint8((uint32(d[2])*a/m + sb) >> 8) d[3] = uint8((uint32(d[3])*a/m + sa) >> 8) } d0 += ddelta s0 += sdelta } } // drawCopySrc copies bytes to dstPix from srcPix. These arguments roughly // correspond to the Pix fields of the image package's concrete image.Image // implementations, but are offset (dstPix is dst.Pix[dpOffset:] not dst.Pix). func drawCopySrc( dstPix []byte, dstStride int, r image.Rectangle, srcPix []byte, srcStride int, sp image.Point, bytesPerRow int) { d0, s0, ddelta, sdelta, dy := 0, 0, dstStride, srcStride, r.Dy() if r.Min.Y > sp.Y { // 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 coordinates because the built-in copy function can handle // overlapping slices. d0 = (dy - 1) * dstStride s0 = (dy - 1) * srcStride ddelta = -dstStride sdelta = -srcStride } for ; dy > 0; dy-- { copy(dstPix[d0:d0+bytesPerRow], srcPix[s0:s0+bytesPerRow]) 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. s := spix[si : si+4 : si+4] // Small cap improves performance, see https://golang.org/issue/27857 sa := uint32(s[3]) * 0x101 sr := uint32(s[0]) * sa / 0xff sg := uint32(s[1]) * sa / 0xff sb := uint32(s[2]) * sa / 0xff d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 dr := uint32(d[0]) dg := uint32(d[1]) db := uint32(d[2]) da := uint32(d[3]) // The 0x101 is here for the same reason as in drawRGBA. a := (m - sa) * 0x101 d[0] = uint8((dr*a/m + sr) >> 8) d[1] = uint8((dg*a/m + sg) >> 8) d[2] = uint8((db*a/m + sb) >> 8) d[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. s := spix[si : si+4 : si+4] // Small cap improves performance, see https://golang.org/issue/27857 sa := uint32(s[3]) * 0x101 sr := uint32(s[0]) * sa / 0xff sg := uint32(s[1]) * sa / 0xff sb := uint32(s[2]) * sa / 0xff d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 d[0] = uint8(sr >> 8) d[1] = uint8(sg >> 8) d[2] = uint8(sb >> 8) d[3] = uint8(sa >> 8) } } } func drawGray(dst *image.RGBA, r image.Rectangle, src *image.Gray, 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) * 1 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+1 { p := spix[si] d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 d[0] = p d[1] = p d[2] = p d[3] = 255 } } } func drawCMYK(dst *image.RGBA, r image.Rectangle, src *image.CMYK, 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 { s := spix[si : si+4 : si+4] // Small cap improves performance, see https://golang.org/issue/27857 d := dpix[i : i+4 : i+4] d[0], d[1], d[2] = color.CMYKToRGB(s[0], s[1], s[2], s[3]) d[3] = 255 } } } 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 // The 0x101 is here for the same reason as in drawRGBA. a := (m - (sa * ma / m)) * 0x101 d := dst.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 d[0] = uint8((uint32(d[0])*a + sr*ma) / m >> 8) d[1] = uint8((uint32(d[1])*a + sg*ma) / m >> 8) d[2] = uint8((uint32(d[2])*a + sb*ma) / m >> 8) d[3] = uint8((uint32(d[3])*a + sa*ma) / m >> 8) } i0 += dst.Stride i1 += dst.Stride mi0 += mask.Stride } } func drawGrayMaskOver(dst *image.RGBA, r image.Rectangle, src *image.Gray, sp image.Point, mask *image.Alpha, mp image.Point) { x0, x1, dx := r.Min.X, r.Max.X, 1 y0, y1, dy := r.Min.Y, r.Max.Y, 1 if 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 { mi := mask.PixOffset(mx, my) ma := uint32(mask.Pix[mi]) ma |= ma << 8 si := src.PixOffset(sx, sy) sy := uint32(src.Pix[si]) sy |= sy << 8 sa := uint32(0xffff) d := dst.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 dr := uint32(d[0]) dg := uint32(d[1]) db := uint32(d[2]) da := uint32(d[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 d[0] = uint8((dr*a + sy*ma) / m >> 8) d[1] = uint8((dg*a + sy*ma) / m >> 8) d[2] = uint8((db*a + sy*ma) / m >> 8) d[3] = uint8((da*a + sa*ma) / m >> 8) } i0 += dy * dst.Stride } } func drawRGBAMaskOver(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.Point, mask *image.Alpha, mp image.Point) { x0, x1, dx := r.Min.X, r.Max.X, 1 y0, y1, dy := r.Min.Y, r.Max.Y, 1 if 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 { mi := mask.PixOffset(mx, my) ma := uint32(mask.Pix[mi]) ma |= ma << 8 si := src.PixOffset(sx, sy) sr := uint32(src.Pix[si+0]) sg := uint32(src.Pix[si+1]) sb := uint32(src.Pix[si+2]) sa := uint32(src.Pix[si+3]) sr |= sr << 8 sg |= sg << 8 sb |= sb << 8 sa |= sa << 8 d := dst.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 dr := uint32(d[0]) dg := uint32(d[1]) db := uint32(d[2]) da := uint32(d[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 d[0] = uint8((dr*a + sr*ma) / m >> 8) d[1] = uint8((dg*a + sg*ma) / m >> 8) d[2] = uint8((db*a + sb*ma) / m >> 8) d[3] = uint8((da*a + sa*ma) / m >> 8) } i0 += dy * dst.Stride } } func drawRGBA64ImageMaskOver(dst *image.RGBA, r image.Rectangle, src image.RGBA64Image, sp image.Point, mask *image.Alpha, mp image.Point) { 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 { mi := mask.PixOffset(mx, my) ma := uint32(mask.Pix[mi]) ma |= ma << 8 srgba := src.RGBA64At(sx, sy) d := dst.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 dr := uint32(d[0]) dg := uint32(d[1]) db := uint32(d[2]) da := uint32(d[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 - (uint32(srgba.A) * ma / m)) * 0x101 d[0] = uint8((dr*a + uint32(srgba.R)*ma) / m >> 8) d[1] = uint8((dg*a + uint32(srgba.G)*ma) / m >> 8) d[2] = uint8((db*a + uint32(srgba.B)*ma) / m >> 8) d[3] = uint8((da*a + uint32(srgba.A)*ma) / m >> 8) } i0 += dy * dst.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 // Try the image.RGBA64Image interface, part of the standard library since // Go 1.17. // // This optimization is similar to how FALLBACK1.17 optimizes FALLBACK1.0 // in DrawMask, except here the concrete type of dst is known to be // *image.RGBA. if src0, _ := src.(image.RGBA64Image); src0 != nil { if mask == nil { if op == Over { 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 { srgba := src0.RGBA64At(sx, sy) d := dst.Pix[i : i+4 : i+4] dr := uint32(d[0]) dg := uint32(d[1]) db := uint32(d[2]) da := uint32(d[3]) a := (m - uint32(srgba.A)) * 0x101 d[0] = uint8((dr*a/m + uint32(srgba.R)) >> 8) d[1] = uint8((dg*a/m + uint32(srgba.G)) >> 8) d[2] = uint8((db*a/m + uint32(srgba.B)) >> 8) d[3] = uint8((da*a/m + uint32(srgba.A)) >> 8) } i0 += dy * dst.Stride } } else { 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 { srgba := src0.RGBA64At(sx, sy) d := dst.Pix[i : i+4 : i+4] d[0] = uint8(srgba.R >> 8) d[1] = uint8(srgba.G >> 8) d[2] = uint8(srgba.B >> 8) d[3] = uint8(srgba.A >> 8) } i0 += dy * dst.Stride } } return } else if mask0, _ := mask.(image.RGBA64Image); mask0 != nil { if op == Over { 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(mask0.RGBA64At(mx, my).A) srgba := src0.RGBA64At(sx, sy) d := dst.Pix[i : i+4 : i+4] dr := uint32(d[0]) dg := uint32(d[1]) db := uint32(d[2]) da := uint32(d[3]) a := (m - (uint32(srgba.A) * ma / m)) * 0x101 d[0] = uint8((dr*a + uint32(srgba.R)*ma) / m >> 8) d[1] = uint8((dg*a + uint32(srgba.G)*ma) / m >> 8) d[2] = uint8((db*a + uint32(srgba.B)*ma) / m >> 8) d[3] = uint8((da*a + uint32(srgba.A)*ma) / m >> 8) } i0 += dy * dst.Stride } } else { 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(mask0.RGBA64At(mx, my).A) srgba := src0.RGBA64At(sx, sy) d := dst.Pix[i : i+4 : i+4] d[0] = uint8(uint32(srgba.R) * ma / m >> 8) d[1] = uint8(uint32(srgba.G) * ma / m >> 8) d[2] = uint8(uint32(srgba.B) * ma / m >> 8) d[3] = uint8(uint32(srgba.A) * ma / m >> 8) } i0 += dy * dst.Stride } } return } } // Use the image.Image interface, part of the standard library since Go // 1.0. // // This is similar to FALLBACK1.0 in DrawMask, except here the concrete // type of dst is known to be *image.RGBA. 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() d := dst.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857 if op == Over { dr := uint32(d[0]) dg := uint32(d[1]) db := uint32(d[2]) da := uint32(d[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 d[0] = uint8((dr*a + sr*ma) / m >> 8) d[1] = uint8((dg*a + sg*ma) / m >> 8) d[2] = uint8((db*a + sb*ma) / m >> 8) d[3] = uint8((da*a + sa*ma) / m >> 8) } else { d[0] = uint8(sr * ma / m >> 8) d[1] = uint8(sg * ma / m >> 8) d[2] = uint8(sb * ma / m >> 8) d[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 } // sqDiff returns the squared-difference of x and y, shifted by 2 so that // adding four of those won't overflow a uint32. // // x and y are both assumed to be in the range [0, 0xffff]. func sqDiff(x, y int32) uint32 { // This is an optimized code relying on the overflow/wrap around // properties of unsigned integers operations guaranteed by the language // spec. See sqDiff from the image/color package for more details. d := uint32(x - y) return (d * d) >> 2 } 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 := [][4]int32(nil), []byte(nil), 0 if p, ok := dst.(*image.Paletted); ok { palette = make([][4]int32, len(p.Palette)) for i, col := range p.Palette { r, g, b, a := col.RGBA() palette[i][0] = int32(r) palette[i][1] = int32(g) palette[i][2] = int32(b) palette[i][3] = int32(a) } 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 [][4]int32 if floydSteinberg { quantErrorCurr = make([][4]int32, r.Dx()+2) quantErrorNext = make([][4]int32, r.Dx()+2) } pxRGBA := func(x, y int) (r, g, b, a uint32) { return src.At(x, y).RGBA() } // Fast paths for special cases to avoid excessive use of the color.Color // interface which escapes to the heap but need to be discovered for // each pixel on r. See also https://golang.org/issues/15759. switch src0 := src.(type) { case *image.RGBA: pxRGBA = func(x, y int) (r, g, b, a uint32) { return src0.RGBAAt(x, y).RGBA() } case *image.NRGBA: pxRGBA = func(x, y int) (r, g, b, a uint32) { return src0.NRGBAAt(x, y).RGBA() } case *image.YCbCr: pxRGBA = func(x, y int) (r, g, b, a uint32) { return src0.YCbCrAt(x, y).RGBA() } } // 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, sa := pxRGBA(sp.X+x, sp.Y+y) er, eg, eb, ea := int32(sr), int32(sg), int32(sb), int32(sa) 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) ea = clamp(ea + quantErrorCurr[x+1][3]/16) } if palette != nil { // Find the closest palette color in Euclidean R,G,B,A space: // the one that minimizes sum-squared-difference. // TODO(nigeltao): consider smarter algorithms. bestIndex, bestSum := 0, uint32(1<<32-1) for index, p := range palette { sum := sqDiff(er, p[0]) + sqDiff(eg, p[1]) + sqDiff(eb, p[2]) + sqDiff(ea, p[3]) if sum < bestSum { bestIndex, bestSum = index, sum if sum == 0 { break } } } pix[y*stride+x] = byte(bestIndex) if !floydSteinberg { continue } er -= palette[bestIndex][0] eg -= palette[bestIndex][1] eb -= palette[bestIndex][2] ea -= palette[bestIndex][3] } else { out.R = uint16(er) out.G = uint16(eg) out.B = uint16(eb) out.A = uint16(ea) // 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, sa = dst.At(r.Min.X+x, r.Min.Y+y).RGBA() er -= int32(sr) eg -= int32(sg) eb -= int32(sb) ea -= int32(sa) } // 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+0][3] += ea * 3 quantErrorNext[x+1][0] += er * 5 quantErrorNext[x+1][1] += eg * 5 quantErrorNext[x+1][2] += eb * 5 quantErrorNext[x+1][3] += ea * 5 quantErrorNext[x+2][0] += er * 1 quantErrorNext[x+2][1] += eg * 1 quantErrorNext[x+2][2] += eb * 1 quantErrorNext[x+2][3] += ea * 1 quantErrorCurr[x+2][0] += er * 7 quantErrorCurr[x+2][1] += eg * 7 quantErrorCurr[x+2][2] += eb * 7 quantErrorCurr[x+2][3] += ea * 7 } // Recycle the quantization error buffers. if floydSteinberg { quantErrorCurr, quantErrorNext = quantErrorNext, quantErrorCurr for i := range quantErrorNext { quantErrorNext[i] = [4]int32{} } } } }