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path: root/src/pkg/image/draw/draw.go
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-rw-r--r--src/pkg/image/draw/draw.go480
1 files changed, 480 insertions, 0 deletions
diff --git a/src/pkg/image/draw/draw.go b/src/pkg/image/draw/draw.go
new file mode 100644
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--- /dev/null
+++ b/src/pkg/image/draw/draw.go
@@ -0,0 +1,480 @@
+// 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
+// in the style of the Plan 9 graphics library
+// (see http://plan9.bell-labs.com/magic/man2html/2/draw)
+// and the X Render extension.
+package draw
+
+import (
+ "image"
+ "image/ycbcr"
+)
+
+// m is the maximum color value returned by image.Color.RGBA.
+const m = 1<<16 - 1
+
+// 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
+)
+
+var zeroColor image.Color = image.AlphaColor{0}
+
+// A draw.Image is an image.Image with a Set method to change a single pixel.
+type Image interface {
+ image.Image
+ Set(x, y int, c image.Color)
+}
+
+// Draw calls DrawMask with a nil mask and an Over op.
+func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point) {
+ DrawMask(dst, r, src, sp, nil, image.ZP, Over)
+}
+
+// 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
+}
+
+// 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.
+ if dst0, ok := dst.(*image.RGBA); ok {
+ if op == Over {
+ if mask == nil {
+ switch src0 := src.(type) {
+ case *image.ColorImage:
+ drawFillOver(dst0, r, src0)
+ return
+ case *image.RGBA:
+ drawCopyOver(dst0, r, src0, sp)
+ return
+ case *image.NRGBA:
+ drawNRGBAOver(dst0, r, src0, sp)
+ return
+ case *ycbcr.YCbCr:
+ drawYCbCr(dst0, r, src0, sp)
+ return
+ }
+ } else if mask0, ok := mask.(*image.Alpha); ok {
+ switch src0 := src.(type) {
+ case *image.ColorImage:
+ drawGlyphOver(dst0, r, src0, mask0, mp)
+ return
+ }
+ }
+ } else {
+ if mask == nil {
+ switch src0 := src.(type) {
+ case *image.ColorImage:
+ drawFillSrc(dst0, r, src0)
+ return
+ case *image.RGBA:
+ drawCopySrc(dst0, r, src0, sp)
+ return
+ case *image.NRGBA:
+ drawNRGBASrc(dst0, r, src0, sp)
+ return
+ case *ycbcr.YCbCr:
+ drawYCbCr(dst0, r, src0, sp)
+ return
+ }
+ }
+ }
+ drawRGBA(dst0, r, src, sp, mask, mp, op)
+ return
+ }
+
+ 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))) {
+ // Rectangles overlap: process backward?
+ 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
+ }
+ }
+
+ var out *image.RGBA64Color
+ 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, zeroColor)
+ }
+ case ma == m && op == Src:
+ dst.Set(x, y, src.At(sx, sy))
+ default:
+ sr, sg, sb, sa := src.At(sx, sy).RGBA()
+ if out == nil {
+ out = new(image.RGBA64Color)
+ }
+ 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)
+ }
+ dst.Set(x, y, out)
+ }
+ }
+ }
+}
+
+func drawFillOver(dst *image.RGBA, r image.Rectangle, src *image.ColorImage) {
+ cr, cg, cb, ca := src.RGBA()
+ // The 0x101 is here for the same reason as in drawRGBA.
+ a := (m - ca) * 0x101
+ x0, x1 := r.Min.X, r.Max.X
+ y0, y1 := r.Min.Y, r.Max.Y
+ for y := y0; y != y1; y++ {
+ dbase := y * dst.Stride
+ dpix := dst.Pix[dbase+x0 : dbase+x1]
+ for i, rgba := range dpix {
+ dr := (uint32(rgba.R)*a)/m + cr
+ dg := (uint32(rgba.G)*a)/m + cg
+ db := (uint32(rgba.B)*a)/m + cb
+ da := (uint32(rgba.A)*a)/m + ca
+ dpix[i] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
+ }
+ }
+}
+
+func drawCopyOver(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.Point) {
+ dx0, dx1 := r.Min.X, r.Max.X
+ dy0, dy1 := r.Min.Y, r.Max.Y
+ nrows := dy1 - dy0
+ sx0, sx1 := sp.X, sp.X+dx1-dx0
+ d0 := dy0*dst.Stride + dx0
+ d1 := dy0*dst.Stride + dx1
+ s0 := sp.Y*src.Stride + sx0
+ s1 := sp.Y*src.Stride + sx1
+ 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, d1-d0, +1
+ } 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 += (nrows - 1) * dst.Stride
+ d1 += (nrows - 1) * dst.Stride
+ s0 += (nrows - 1) * src.Stride
+ s1 += (nrows - 1) * src.Stride
+ ddelta = -dst.Stride
+ sdelta = -src.Stride
+ i0, i1, idelta = d1-d0-1, -1, -1
+ }
+ for ; nrows > 0; nrows-- {
+ dpix := dst.Pix[d0:d1]
+ spix := src.Pix[s0:s1]
+ for i := i0; i != i1; i += idelta {
+ // For unknown reasons, even though both dpix[i] and spix[i] are
+ // image.RGBAColors, on an x86 CPU it seems fastest to call RGBA
+ // for the source but to do it manually for the destination.
+ sr, sg, sb, sa := spix[i].RGBA()
+ rgba := dpix[i]
+ dr := uint32(rgba.R)
+ dg := uint32(rgba.G)
+ db := uint32(rgba.B)
+ da := uint32(rgba.A)
+ // The 0x101 is here for the same reason as in drawRGBA.
+ a := (m - sa) * 0x101
+ dr = (dr*a)/m + sr
+ dg = (dg*a)/m + sg
+ db = (db*a)/m + sb
+ da = (da*a)/m + sa
+ dpix[i] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
+ }
+ d0 += ddelta
+ d1 += ddelta
+ s0 += sdelta
+ s1 += sdelta
+ }
+}
+
+func drawNRGBAOver(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image.Point) {
+ for y, sy := r.Min.Y, sp.Y; y != r.Max.Y; y, sy = y+1, sy+1 {
+ dpix := dst.Pix[y*dst.Stride : (y+1)*dst.Stride]
+ spix := src.Pix[sy*src.Stride : (sy+1)*src.Stride]
+ for x, sx := r.Min.X, sp.X; x != r.Max.X; x, sx = x+1, sx+1 {
+ // Convert from non-premultiplied color to pre-multiplied color.
+ // The order of operations here is to match the NRGBAColor.RGBA
+ // method in image/color.go.
+ snrgba := spix[sx]
+ sa := uint32(snrgba.A)
+ sr := uint32(snrgba.R) * 0x101 * sa / 0xff
+ sg := uint32(snrgba.G) * 0x101 * sa / 0xff
+ sb := uint32(snrgba.B) * 0x101 * sa / 0xff
+ sa *= 0x101
+
+ rgba := dpix[x]
+ dr := uint32(rgba.R)
+ dg := uint32(rgba.G)
+ db := uint32(rgba.B)
+ da := uint32(rgba.A)
+ a := (m - sa) * 0x101
+ dr = (dr*a + sr*m) / m
+ dg = (dg*a + sg*m) / m
+ db = (db*a + sb*m) / m
+ da = (da*a + sa*m) / m
+ dpix[x] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
+ }
+ }
+}
+
+func drawGlyphOver(dst *image.RGBA, r image.Rectangle, src *image.ColorImage, mask *image.Alpha, mp image.Point) {
+ x0, x1 := r.Min.X, r.Max.X
+ y0, y1 := r.Min.Y, r.Max.Y
+ cr, cg, cb, ca := src.RGBA()
+ for y, my := y0, mp.Y; y != y1; y, my = y+1, my+1 {
+ dbase := y * dst.Stride
+ dpix := dst.Pix[dbase+x0 : dbase+x1]
+ mbase := my * mask.Stride
+ mpix := mask.Pix[mbase+mp.X:]
+ for i, rgba := range dpix {
+ ma := uint32(mpix[i].A)
+ if ma == 0 {
+ continue
+ }
+ ma |= ma << 8
+ dr := uint32(rgba.R)
+ dg := uint32(rgba.G)
+ db := uint32(rgba.B)
+ da := uint32(rgba.A)
+ // The 0x101 is here for the same reason as in drawRGBA.
+ a := (m - (ca * ma / m)) * 0x101
+ dr = (dr*a + cr*ma) / m
+ dg = (dg*a + cg*ma) / m
+ db = (db*a + cb*ma) / m
+ da = (da*a + ca*ma) / m
+ dpix[i] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
+ }
+ }
+}
+
+func drawFillSrc(dst *image.RGBA, r image.Rectangle, src *image.ColorImage) {
+ if r.Dy() < 1 {
+ return
+ }
+ cr, cg, cb, ca := src.RGBA()
+ color := image.RGBAColor{uint8(cr >> 8), uint8(cg >> 8), uint8(cb >> 8), uint8(ca >> 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.
+ dx0, dx1 := r.Min.X, r.Max.X
+ dy0, dy1 := r.Min.Y, r.Max.Y
+ dbase := dy0 * dst.Stride
+ i0, i1 := dbase+dx0, dbase+dx1
+ firstRow := dst.Pix[i0:i1]
+ for i := range firstRow {
+ firstRow[i] = color
+ }
+ for y := dy0 + 1; y < dy1; y++ {
+ i0 += dst.Stride
+ i1 += dst.Stride
+ copy(dst.Pix[i0:i1], firstRow)
+ }
+}
+
+func drawCopySrc(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.Point) {
+ dx0, dx1 := r.Min.X, r.Max.X
+ dy0, dy1 := r.Min.Y, r.Max.Y
+ nrows := dy1 - dy0
+ sx0, sx1 := sp.X, sp.X+dx1-dx0
+ d0 := dy0*dst.Stride + dx0
+ d1 := dy0*dst.Stride + dx1
+ s0 := sp.Y*src.Stride + sx0
+ s1 := sp.Y*src.Stride + sx1
+ 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 += (nrows - 1) * dst.Stride
+ d1 += (nrows - 1) * dst.Stride
+ s0 += (nrows - 1) * src.Stride
+ s1 += (nrows - 1) * src.Stride
+ ddelta = -dst.Stride
+ sdelta = -src.Stride
+ }
+ for ; nrows > 0; nrows-- {
+ copy(dst.Pix[d0:d1], src.Pix[s0:s1])
+ d0 += ddelta
+ d1 += ddelta
+ s0 += sdelta
+ s1 += sdelta
+ }
+}
+
+func drawNRGBASrc(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image.Point) {
+ for y, sy := r.Min.Y, sp.Y; y != r.Max.Y; y, sy = y+1, sy+1 {
+ dpix := dst.Pix[y*dst.Stride : (y+1)*dst.Stride]
+ spix := src.Pix[sy*src.Stride : (sy+1)*src.Stride]
+ for x, sx := r.Min.X, sp.X; x != r.Max.X; x, sx = x+1, sx+1 {
+ // Convert from non-premultiplied color to pre-multiplied color.
+ // The order of operations here is to match the NRGBAColor.RGBA
+ // method in image/color.go.
+ snrgba := spix[sx]
+ sa := uint32(snrgba.A)
+ sr := uint32(snrgba.R) * 0x101 * sa / 0xff
+ sg := uint32(snrgba.G) * 0x101 * sa / 0xff
+ sb := uint32(snrgba.B) * 0x101 * sa / 0xff
+ sa *= 0x101
+
+ dpix[x] = image.RGBAColor{uint8(sr >> 8), uint8(sg >> 8), uint8(sb >> 8), uint8(sa >> 8)}
+ }
+ }
+}
+
+func drawYCbCr(dst *image.RGBA, r image.Rectangle, src *ycbcr.YCbCr, sp image.Point) {
+ // A YCbCr image is always fully opaque, and so if the mask is implicitly nil
+ // (i.e. fully opaque) then the op is effectively always Src.
+ var (
+ yy, cb, cr uint8
+ rr, gg, bb uint8
+ )
+ switch src.SubsampleRatio {
+ case ycbcr.SubsampleRatio422:
+ for y, sy := r.Min.Y, sp.Y; y != r.Max.Y; y, sy = y+1, sy+1 {
+ dpix := dst.Pix[y*dst.Stride : (y+1)*dst.Stride]
+ for x, sx := r.Min.X, sp.X; x != r.Max.X; x, sx = x+1, sx+1 {
+ i := sx / 2
+ yy = src.Y[sy*src.YStride+sx]
+ cb = src.Cb[sy*src.CStride+i]
+ cr = src.Cr[sy*src.CStride+i]
+ rr, gg, bb = ycbcr.YCbCrToRGB(yy, cb, cr)
+ dpix[x] = image.RGBAColor{rr, gg, bb, 255}
+ }
+ }
+ case ycbcr.SubsampleRatio420:
+ for y, sy := r.Min.Y, sp.Y; y != r.Max.Y; y, sy = y+1, sy+1 {
+ dpix := dst.Pix[y*dst.Stride : (y+1)*dst.Stride]
+ for x, sx := r.Min.X, sp.X; x != r.Max.X; x, sx = x+1, sx+1 {
+ i, j := sx/2, sy/2
+ yy = src.Y[sy*src.YStride+sx]
+ cb = src.Cb[j*src.CStride+i]
+ cr = src.Cr[j*src.CStride+i]
+ rr, gg, bb = ycbcr.YCbCrToRGB(yy, cb, cr)
+ dpix[x] = image.RGBAColor{rr, gg, bb, 255}
+ }
+ }
+ default:
+ // Default to 4:4:4 subsampling.
+ for y, sy := r.Min.Y, sp.Y; y != r.Max.Y; y, sy = y+1, sy+1 {
+ dpix := dst.Pix[y*dst.Stride : (y+1)*dst.Stride]
+ for x, sx := r.Min.X, sp.X; x != r.Max.X; x, sx = x+1, sx+1 {
+ yy = src.Y[sy*src.YStride+sx]
+ cb = src.Cb[sy*src.CStride+sx]
+ cr = src.Cr[sy*src.CStride+sx]
+ rr, gg, bb = ycbcr.YCbCrToRGB(yy, cb, cr)
+ dpix[x] = image.RGBAColor{rr, gg, bb, 255}
+ }
+ }
+ }
+}
+
+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
+ 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
+ dpix := dst.Pix[y*dst.Stride : (y+1)*dst.Stride]
+ 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()
+ }
+ sr, sg, sb, sa := src.At(sx, sy).RGBA()
+ var dr, dg, db, da uint32
+ if op == Over {
+ rgba := dpix[x]
+ dr = uint32(rgba.R)
+ dg = uint32(rgba.G)
+ db = uint32(rgba.B)
+ da = uint32(rgba.A)
+ // 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
+ dr = (dr*a + sr*ma) / m
+ dg = (dg*a + sg*ma) / m
+ db = (db*a + sb*ma) / m
+ da = (da*a + sa*ma) / m
+ } else {
+ dr = sr * ma / m
+ dg = sg * ma / m
+ db = sb * ma / m
+ da = sa * ma / m
+ }
+ dpix[x] = image.RGBAColor{uint8(dr >> 8), uint8(dg >> 8), uint8(db >> 8), uint8(da >> 8)}
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2025-04-11 23:13:23 +0000