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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [image/] [draw/] [draw.go] - Rev 861
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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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