1 files changed, 493 insertions, 0 deletions
diff --git a/libgo/go/image/draw/draw.go b/libgo/go/image/draw/draw.go
new file mode 100644
index 00000000000..a748ff8c77a
--- /dev/null
+++ b/libgo/go/image/draw/draw.go
@@ -0,0 +1,493 @@
+// 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.
+func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op) {
+	DrawMask(dst, r, src, sp, nil, image.ZP, op)
+}
+
+// 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) {
+	sr, sg, sb, sa := src.RGBA()
+	// The 0x101 is here for the same reason as in drawRGBA.
+	a := (m - sa) * 0x101
+	i0 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
+	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.ColorImage) {
+	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 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
+	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 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
+	s0 := (sp.Y-src.Rect.Min.Y)*src.Stride + (sp.X-src.Rect.Min.X)*4
+	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 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
+	s0 := (sp.Y-src.Rect.Min.Y)*src.Stride + (sp.X-src.Rect.Min.X)*4
+	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 *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
+	)
+	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 ycbcr.SubsampleRatio422:
+		for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
+			dpix := dst.Pix[y*dst.Stride:]
+			for x, sx := x0, sp.X; x != x1; x, sx = x+4, 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+0] = rr
+				dpix[x+1] = gg
+				dpix[x+2] = bb
+				dpix[x+3] = 255
+			}
+		}
+	case ycbcr.SubsampleRatio420:
+		for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
+			dpix := dst.Pix[y*dst.Stride:]
+			for x, sx := x0, sp.X; x != x1; x, sx = x+4, 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+0] = rr
+				dpix[x+1] = gg
+				dpix[x+2] = bb
+				dpix[x+3] = 255
+			}
+		}
+	default:
+		// Default to 4:4:4 subsampling.
+		for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
+			dpix := dst.Pix[y*dst.Stride:]
+			for x, sx := x0, sp.X; x != x1; x, sx = x+4, 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+0] = rr
+				dpix[x+1] = gg
+				dpix[x+2] = bb
+				dpix[x+3] = 255
+			}
+		}
+	}
+}
+
+func drawGlyphOver(dst *image.RGBA, r image.Rectangle, src *image.ColorImage, mask *image.Alpha, mp image.Point) {
+	i0 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
+	i1 := i0 + r.Dx()*4
+	mi0 := (mp.Y-mask.Rect.Min.Y)*mask.Stride + mp.X - mask.Rect.Min.X
+	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 := (y0-dst.Rect.Min.Y)*dst.Stride + (x0-dst.Rect.Min.X)*4
+	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
+	}
+}