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// 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://blog.golang.org/2011/09/go-imagedraw-package.html
package draw
 
import (
        "image"
        "image/color"
)
 
// 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
)
 
// 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 color.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.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:
                                        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:
                                        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 *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 out == nil {
                                        out = new(color.RGBA64)
                                }
                                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.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) {
        // 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.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
                        }
                }
        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:]
                        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
                        }
                }
        }
}
 
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
        }
}

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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [image/] [draw/] [draw.go] - Blame information for rev 747

Line No.	Rev	Author	Line
1	747	jeremybenn	`// Copyright 2009 The Go Authors. All rights reserved.`
2			`// Use of this source code is governed by a BSD-style`
3			`// license that can be found in the LICENSE file.`
4
5			`// Package draw provides image composition functions.`
6			`//`
7			`// See "The Go image/draw package" for an introduction to this package:`
8			`// http://blog.golang.org/2011/09/go-imagedraw-package.html`
9			`package draw`
10
11			`import (`
12			`"image"`
13			`"image/color"`
14			`)`
15
16			`// m is the maximum color value returned by image.Color.RGBA.`
17			`const m = 1<<16 - 1`
18
19			`// Op is a Porter-Duff compositing operator.`
20			`type Op int`
21
22			`const (`
23			// Over specifies ``(src in mask) over dst''.
24			`Over Op = iota`
25			// Src specifies ``src in mask''.
26			`Src`
27			`)`
28
29			`// A draw.Image is an image.Image with a Set method to change a single pixel.`
30			`type Image interface {`
31			`image.Image`
32			`Set(x, y int, c color.Color)`
33			`}`
34
35			`// Draw calls DrawMask with a nil mask.`
36			`func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op) {`
37			`DrawMask(dst, r, src, sp, nil, image.ZP, op)`
38			`}`
39
40			`// clip clips r against each image's bounds (after translating into the`
41			`// destination image's co-ordinate space) and shifts the points sp and mp by`
42			`// the same amount as the change in r.Min.`
43			`func clip(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp *image.Point) {`
44			`orig := r.Min`
45			`*r = r.Intersect(dst.Bounds())`
46			`r = r.Intersect(src.Bounds().Add(orig.Sub(sp)))`
47			`if mask != nil {`
48			`r = r.Intersect(mask.Bounds().Add(orig.Sub(mp)))`
49			`}`
50			`dx := r.Min.X - orig.X`
51			`dy := r.Min.Y - orig.Y`
52			`if dx == 0 && dy == 0 {`
53			`return`
54			`}`
55			`(*sp).X += dx`
56			`(*sp).Y += dy`
57			`(*mp).X += dx`
58			`(*mp).Y += dy`
59			`}`
60
61			`// DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r`
62			`// in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque.`
63			`func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op) {`
64			`clip(dst, &r, src, &sp, mask, &mp)`
65			`if r.Empty() {`
66			`return`
67			`}`
68
69			`// Fast paths for special cases. If none of them apply, then we fall back to a general but slow implementation.`
70			`if dst0, ok := dst.(*image.RGBA); ok {`
71			`if op == Over {`
72			`if mask == nil {`
73			`switch src0 := src.(type) {`
74			`case *image.Uniform:`
75			`drawFillOver(dst0, r, src0)`
76			`return`
77			`case *image.RGBA:`
78			`drawCopyOver(dst0, r, src0, sp)`
79			`return`
80			`case *image.NRGBA:`
81			`drawNRGBAOver(dst0, r, src0, sp)`
82			`return`
83			`case *image.YCbCr:`
84			`drawYCbCr(dst0, r, src0, sp)`
85			`return`
86			`}`
87			`} else if mask0, ok := mask.(*image.Alpha); ok {`
88			`switch src0 := src.(type) {`
89			`case *image.Uniform:`
90			`drawGlyphOver(dst0, r, src0, mask0, mp)`
91			`return`
92			`}`
93			`}`
94			`} else {`
95			`if mask == nil {`
96			`switch src0 := src.(type) {`
97			`case *image.Uniform:`
98			`drawFillSrc(dst0, r, src0)`
99			`return`
100			`case *image.RGBA:`
101			`drawCopySrc(dst0, r, src0, sp)`
102			`return`
103			`case *image.NRGBA:`
104			`drawNRGBASrc(dst0, r, src0, sp)`
105			`return`
106			`case *image.YCbCr:`
107			`drawYCbCr(dst0, r, src0, sp)`
108			`return`
109			`}`
110			`}`
111			`}`
112			`drawRGBA(dst0, r, src, sp, mask, mp, op)`
113			`return`
114			`}`
115
116			`x0, x1, dx := r.Min.X, r.Max.X, 1`
117			`y0, y1, dy := r.Min.Y, r.Max.Y, 1`
118			`if image.Image(dst) == src && r.Overlaps(r.Add(sp.Sub(r.Min))) {`
119			`// Rectangles overlap: process backward?`
120			`if sp.Y < r.Min.Y \|\| sp.Y == r.Min.Y && sp.X < r.Min.X {`
121			`x0, x1, dx = x1-1, x0-1, -1`
122			`y0, y1, dy = y1-1, y0-1, -1`
123			`}`
124			`}`
125
126			`var out *color.RGBA64`
127			`sy := sp.Y + y0 - r.Min.Y`
128			`my := mp.Y + y0 - r.Min.Y`
129			`for y := y0; y != y1; y, sy, my = y+dy, sy+dy, my+dy {`
130			`sx := sp.X + x0 - r.Min.X`
131			`mx := mp.X + x0 - r.Min.X`
132			`for x := x0; x != x1; x, sx, mx = x+dx, sx+dx, mx+dx {`
133			`ma := uint32(m)`
134			`if mask != nil {`
135			`_, _, _, ma = mask.At(mx, my).RGBA()`
136			`}`
137			`switch {`
138			`case ma == 0:`
139			`if op == Over {`
140			`// No-op.`
141			`} else {`
142			`dst.Set(x, y, color.Transparent)`
143			`}`
144			`case ma == m && op == Src:`
145			`dst.Set(x, y, src.At(sx, sy))`
146			`default:`
147			`sr, sg, sb, sa := src.At(sx, sy).RGBA()`
148			`if out == nil {`
149			`out = new(color.RGBA64)`
150			`}`
151			`if op == Over {`
152			`dr, dg, db, da := dst.At(x, y).RGBA()`
153			`a := m - (sa * ma / m)`
154			`out.R = uint16((dra + srma) / m)`
155			`out.G = uint16((dga + sgma) / m)`
156			`out.B = uint16((dba + sbma) / m)`
157			`out.A = uint16((daa + sama) / m)`
158			`} else {`
159			`out.R = uint16(sr * ma / m)`
160			`out.G = uint16(sg * ma / m)`
161			`out.B = uint16(sb * ma / m)`
162			`out.A = uint16(sa * ma / m)`
163			`}`
164			`dst.Set(x, y, out)`
165			`}`
166			`}`
167			`}`
168			`}`
169
170			`func drawFillOver(dst image.RGBA, r image.Rectangle, src image.Uniform) {`
171			`sr, sg, sb, sa := src.RGBA()`
172			`// The 0x101 is here for the same reason as in drawRGBA.`
173			`a := (m - sa) * 0x101`
174			`i0 := dst.PixOffset(r.Min.X, r.Min.Y)`
175			`i1 := i0 + r.Dx()*4`
176			`for y := r.Min.Y; y != r.Max.Y; y++ {`
177			`for i := i0; i < i1; i += 4 {`
178			`dr := uint32(dst.Pix[i+0])`
179			`dg := uint32(dst.Pix[i+1])`
180			`db := uint32(dst.Pix[i+2])`
181			`da := uint32(dst.Pix[i+3])`
182
183			`dst.Pix[i+0] = uint8((dr*a/m + sr) >> 8)`
184			`dst.Pix[i+1] = uint8((dg*a/m + sg) >> 8)`
185			`dst.Pix[i+2] = uint8((db*a/m + sb) >> 8)`
186			`dst.Pix[i+3] = uint8((da*a/m + sa) >> 8)`
187			`}`
188			`i0 += dst.Stride`
189			`i1 += dst.Stride`
190			`}`
191			`}`
192
193			`func drawFillSrc(dst image.RGBA, r image.Rectangle, src image.Uniform) {`
194			`sr, sg, sb, sa := src.RGBA()`
195			`// The built-in copy function is faster than a straightforward for loop to fill the destination with`
196			`// the color, but copy requires a slice source. We therefore use a for loop to fill the first row, and`
197			`// then use the first row as the slice source for the remaining rows.`
198			`i0 := dst.PixOffset(r.Min.X, r.Min.Y)`
199			`i1 := i0 + r.Dx()*4`
200			`for i := i0; i < i1; i += 4 {`
201			`dst.Pix[i+0] = uint8(sr >> 8)`
202			`dst.Pix[i+1] = uint8(sg >> 8)`
203			`dst.Pix[i+2] = uint8(sb >> 8)`
204			`dst.Pix[i+3] = uint8(sa >> 8)`
205			`}`
206			`firstRow := dst.Pix[i0:i1]`
207			`for y := r.Min.Y + 1; y < r.Max.Y; y++ {`
208			`i0 += dst.Stride`
209			`i1 += dst.Stride`
210			`copy(dst.Pix[i0:i1], firstRow)`
211			`}`
212			`}`
213
214			`func drawCopyOver(dst image.RGBA, r image.Rectangle, src image.RGBA, sp image.Point) {`
215			`dx, dy := r.Dx(), r.Dy()`
216			`d0 := dst.PixOffset(r.Min.X, r.Min.Y)`
217			`s0 := src.PixOffset(sp.X, sp.Y)`
218			`var (`
219			`ddelta, sdelta int`
220			`i0, i1, idelta int`
221			`)`
222			`if r.Min.Y < sp.Y \|\| r.Min.Y == sp.Y && r.Min.X <= sp.X {`
223			`ddelta = dst.Stride`
224			`sdelta = src.Stride`
225			`i0, i1, idelta = 0, dx*4, +4`
226			`} else {`
227			`// If the source start point is higher than the destination start point, or equal height but to the left,`
228			`// then we compose the rows in right-to-left, bottom-up order instead of left-to-right, top-down.`
229			`d0 += (dy - 1) * dst.Stride`
230			`s0 += (dy - 1) * src.Stride`
231			`ddelta = -dst.Stride`
232			`sdelta = -src.Stride`
233			`i0, i1, idelta = (dx-1)*4, -4, -4`
234			`}`
235			`for ; dy > 0; dy-- {`
236			`dpix := dst.Pix[d0:]`
237			`spix := src.Pix[s0:]`
238			`for i := i0; i != i1; i += idelta {`
239			`sr := uint32(spix[i+0]) * 0x101`
240			`sg := uint32(spix[i+1]) * 0x101`
241			`sb := uint32(spix[i+2]) * 0x101`
242			`sa := uint32(spix[i+3]) * 0x101`
243
244			`dr := uint32(dpix[i+0])`
245			`dg := uint32(dpix[i+1])`
246			`db := uint32(dpix[i+2])`
247			`da := uint32(dpix[i+3])`
248
249			`// The 0x101 is here for the same reason as in drawRGBA.`
250			`a := (m - sa) * 0x101`
251
252			`dpix[i+0] = uint8((dr*a/m + sr) >> 8)`
253			`dpix[i+1] = uint8((dg*a/m + sg) >> 8)`
254			`dpix[i+2] = uint8((db*a/m + sb) >> 8)`
255			`dpix[i+3] = uint8((da*a/m + sa) >> 8)`
256			`}`
257			`d0 += ddelta`
258			`s0 += sdelta`
259			`}`
260			`}`
261
262			`func drawCopySrc(dst image.RGBA, r image.Rectangle, src image.RGBA, sp image.Point) {`
263			`n, dy := 4*r.Dx(), r.Dy()`
264			`d0 := dst.PixOffset(r.Min.X, r.Min.Y)`
265			`s0 := src.PixOffset(sp.X, sp.Y)`
266			`var ddelta, sdelta int`
267			`if r.Min.Y <= sp.Y {`
268			`ddelta = dst.Stride`
269			`sdelta = src.Stride`
270			`} else {`
271			`// If the source start point is higher than the destination start point, then we compose the rows`
272			`// in bottom-up order instead of top-down. Unlike the drawCopyOver function, we don't have to`
273			`// check the x co-ordinates because the built-in copy function can handle overlapping slices.`
274			`d0 += (dy - 1) * dst.Stride`
275			`s0 += (dy - 1) * src.Stride`
276			`ddelta = -dst.Stride`
277			`sdelta = -src.Stride`
278			`}`
279			`for ; dy > 0; dy-- {`
280			`copy(dst.Pix[d0:d0+n], src.Pix[s0:s0+n])`
281			`d0 += ddelta`
282			`s0 += sdelta`
283			`}`
284			`}`
285
286			`func drawNRGBAOver(dst image.RGBA, r image.Rectangle, src image.NRGBA, sp image.Point) {`
287			`i0 := (r.Min.X - dst.Rect.Min.X) * 4`
288			`i1 := (r.Max.X - dst.Rect.Min.X) * 4`
289			`si0 := (sp.X - src.Rect.Min.X) * 4`
290			`yMax := r.Max.Y - dst.Rect.Min.Y`
291
292			`y := r.Min.Y - dst.Rect.Min.Y`
293			`sy := sp.Y - src.Rect.Min.Y`
294			`for ; y != yMax; y, sy = y+1, sy+1 {`
295			`dpix := dst.Pix[y*dst.Stride:]`
296			`spix := src.Pix[sy*src.Stride:]`
297
298			`for i, si := i0, si0; i < i1; i, si = i+4, si+4 {`
299			`// Convert from non-premultiplied color to pre-multiplied color.`
300			`sa := uint32(spix[si+3]) * 0x101`
301			`sr := uint32(spix[si+0]) * sa / 0xff`
302			`sg := uint32(spix[si+1]) * sa / 0xff`
303			`sb := uint32(spix[si+2]) * sa / 0xff`
304
305			`dr := uint32(dpix[i+0])`
306			`dg := uint32(dpix[i+1])`
307			`db := uint32(dpix[i+2])`
308			`da := uint32(dpix[i+3])`
309
310			`// The 0x101 is here for the same reason as in drawRGBA.`
311			`a := (m - sa) * 0x101`
312
313			`dpix[i+0] = uint8((dr*a/m + sr) >> 8)`
314			`dpix[i+1] = uint8((dg*a/m + sg) >> 8)`
315			`dpix[i+2] = uint8((db*a/m + sb) >> 8)`
316			`dpix[i+3] = uint8((da*a/m + sa) >> 8)`
317			`}`
318			`}`
319			`}`
320
321			`func drawNRGBASrc(dst image.RGBA, r image.Rectangle, src image.NRGBA, sp image.Point) {`
322			`i0 := (r.Min.X - dst.Rect.Min.X) * 4`
323			`i1 := (r.Max.X - dst.Rect.Min.X) * 4`
324			`si0 := (sp.X - src.Rect.Min.X) * 4`
325			`yMax := r.Max.Y - dst.Rect.Min.Y`
326
327			`y := r.Min.Y - dst.Rect.Min.Y`
328			`sy := sp.Y - src.Rect.Min.Y`
329			`for ; y != yMax; y, sy = y+1, sy+1 {`
330			`dpix := dst.Pix[y*dst.Stride:]`
331			`spix := src.Pix[sy*src.Stride:]`
332
333			`for i, si := i0, si0; i < i1; i, si = i+4, si+4 {`
334			`// Convert from non-premultiplied color to pre-multiplied color.`
335			`sa := uint32(spix[si+3]) * 0x101`
336			`sr := uint32(spix[si+0]) * sa / 0xff`
337			`sg := uint32(spix[si+1]) * sa / 0xff`
338			`sb := uint32(spix[si+2]) * sa / 0xff`
339
340			`dpix[i+0] = uint8(sr >> 8)`
341			`dpix[i+1] = uint8(sg >> 8)`
342			`dpix[i+2] = uint8(sb >> 8)`
343			`dpix[i+3] = uint8(sa >> 8)`
344			`}`
345			`}`
346			`}`
347
348			`func drawYCbCr(dst image.RGBA, r image.Rectangle, src image.YCbCr, sp image.Point) {`
349			`// An image.YCbCr is always fully opaque, and so if the mask is implicitly nil`
350			`// (i.e. fully opaque) then the op is effectively always Src.`
351			`x0 := (r.Min.X - dst.Rect.Min.X) * 4`
352			`x1 := (r.Max.X - dst.Rect.Min.X) * 4`
353			`y0 := r.Min.Y - dst.Rect.Min.Y`
354			`y1 := r.Max.Y - dst.Rect.Min.Y`
355			`switch src.SubsampleRatio {`
356			`case image.YCbCrSubsampleRatio422:`
357			`for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {`
358			`dpix := dst.Pix[y*dst.Stride:]`
359			`yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)`
360			`ciBase := (sy-src.Rect.Min.Y)*src.CStride - src.Rect.Min.X/2`
361			`for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {`
362			`ci := ciBase + sx/2`
363			`rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])`
364			`dpix[x+0] = rr`
365			`dpix[x+1] = gg`
366			`dpix[x+2] = bb`
367			`dpix[x+3] = 255`
368			`}`
369			`}`
370			`case image.YCbCrSubsampleRatio420:`
371			`for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {`
372			`dpix := dst.Pix[y*dst.Stride:]`
373			`yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)`
374			`ciBase := (sy/2-src.Rect.Min.Y/2)*src.CStride - src.Rect.Min.X/2`
375			`for x, sx := x0, sp.X; x != x1; x, sx, yi = x+4, sx+1, yi+1 {`
376			`ci := ciBase + sx/2`
377			`rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])`
378			`dpix[x+0] = rr`
379			`dpix[x+1] = gg`
380			`dpix[x+2] = bb`
381			`dpix[x+3] = 255`
382			`}`
383			`}`
384			`default:`
385			`// Default to 4:4:4 subsampling.`
386			`for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {`
387			`dpix := dst.Pix[y*dst.Stride:]`
388			`yi := (sy-src.Rect.Min.Y)*src.YStride + (sp.X - src.Rect.Min.X)`
389			`ci := (sy-src.Rect.Min.Y)*src.CStride + (sp.X - src.Rect.Min.X)`
390			`for x := x0; x != x1; x, yi, ci = x+4, yi+1, ci+1 {`
391			`rr, gg, bb := color.YCbCrToRGB(src.Y[yi], src.Cb[ci], src.Cr[ci])`
392			`dpix[x+0] = rr`
393			`dpix[x+1] = gg`
394			`dpix[x+2] = bb`
395			`dpix[x+3] = 255`
396			`}`
397			`}`
398			`}`
399			`}`
400
401			`func drawGlyphOver(dst image.RGBA, r image.Rectangle, src image.Uniform, mask *image.Alpha, mp image.Point) {`
402			`i0 := dst.PixOffset(r.Min.X, r.Min.Y)`
403			`i1 := i0 + r.Dx()*4`
404			`mi0 := mask.PixOffset(mp.X, mp.Y)`
405			`sr, sg, sb, sa := src.RGBA()`
406			`for y, my := r.Min.Y, mp.Y; y != r.Max.Y; y, my = y+1, my+1 {`
407			`for i, mi := i0, mi0; i < i1; i, mi = i+4, mi+1 {`
408			`ma := uint32(mask.Pix[mi])`
409			`if ma == 0 {`
410			`continue`
411			`}`
412			`ma \|= ma << 8`
413
414			`dr := uint32(dst.Pix[i+0])`
415			`dg := uint32(dst.Pix[i+1])`
416			`db := uint32(dst.Pix[i+2])`
417			`da := uint32(dst.Pix[i+3])`
418
419			`// The 0x101 is here for the same reason as in drawRGBA.`
420			`a := (m - (sa * ma / m)) * 0x101`
421
422			`dst.Pix[i+0] = uint8((dra + srma) / m >> 8)`
423			`dst.Pix[i+1] = uint8((dga + sgma) / m >> 8)`
424			`dst.Pix[i+2] = uint8((dba + sbma) / m >> 8)`
425			`dst.Pix[i+3] = uint8((daa + sama) / m >> 8)`
426			`}`
427			`i0 += dst.Stride`
428			`i1 += dst.Stride`
429			`mi0 += mask.Stride`
430			`}`
431			`}`
432
433			`func drawRGBA(dst *image.RGBA, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op) {`
434			`x0, x1, dx := r.Min.X, r.Max.X, 1`
435			`y0, y1, dy := r.Min.Y, r.Max.Y, 1`
436			`if image.Image(dst) == src && r.Overlaps(r.Add(sp.Sub(r.Min))) {`
437			`if sp.Y < r.Min.Y \|\| sp.Y == r.Min.Y && sp.X < r.Min.X {`
438			`x0, x1, dx = x1-1, x0-1, -1`
439			`y0, y1, dy = y1-1, y0-1, -1`
440			`}`
441			`}`
442
443			`sy := sp.Y + y0 - r.Min.Y`
444			`my := mp.Y + y0 - r.Min.Y`
445			`sx0 := sp.X + x0 - r.Min.X`
446			`mx0 := mp.X + x0 - r.Min.X`
447			`sx1 := sx0 + (x1 - x0)`
448			`i0 := dst.PixOffset(x0, y0)`
449			`di := dx * 4`
450			`for y := y0; y != y1; y, sy, my = y+dy, sy+dy, my+dy {`
451			`for i, sx, mx := i0, sx0, mx0; sx != sx1; i, sx, mx = i+di, sx+dx, mx+dx {`
452			`ma := uint32(m)`
453			`if mask != nil {`
454			`_, _, _, ma = mask.At(mx, my).RGBA()`
455			`}`
456			`sr, sg, sb, sa := src.At(sx, sy).RGBA()`
457			`if op == Over {`
458			`dr := uint32(dst.Pix[i+0])`
459			`dg := uint32(dst.Pix[i+1])`
460			`db := uint32(dst.Pix[i+2])`
461			`da := uint32(dst.Pix[i+3])`
462
463			`// dr, dg, db and da are all 8-bit color at the moment, ranging in [0,255].`
464			`// We work in 16-bit color, and so would normally do:`
465			`// dr \|= dr << 8`
466			`// and similarly for dg, db and da, but instead we multiply a`
467			`// (which is a 16-bit color, ranging in [0,65535]) by 0x101.`
468			`// This yields the same result, but is fewer arithmetic operations.`
469			`a := (m - (sa * ma / m)) * 0x101`
470
471			`dst.Pix[i+0] = uint8((dra + srma) / m >> 8)`
472			`dst.Pix[i+1] = uint8((dga + sgma) / m >> 8)`
473			`dst.Pix[i+2] = uint8((dba + sbma) / m >> 8)`
474			`dst.Pix[i+3] = uint8((daa + sama) / m >> 8)`
475
476			`} else {`
477			`dst.Pix[i+0] = uint8(sr * ma / m >> 8)`
478			`dst.Pix[i+1] = uint8(sg * ma / m >> 8)`
479			`dst.Pix[i+2] = uint8(sb * ma / m >> 8)`
480			`dst.Pix[i+3] = uint8(sa * ma / m >> 8)`
481			`}`
482			`}`
483			`i0 += dy * dst.Stride`
484			`}`
485			`}`