494 lines
14 KiB
Go
494 lines
14 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package draw provides image composition functions
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// in the style of the Plan 9 graphics library
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// (see http://plan9.bell-labs.com/magic/man2html/2/draw)
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// and the X Render extension.
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package draw
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import (
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"image"
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"image/ycbcr"
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)
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// m is the maximum color value returned by image.Color.RGBA.
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const m = 1<<16 - 1
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// Op is a Porter-Duff compositing operator.
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type Op int
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const (
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// Over specifies ``(src in mask) over dst''.
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Over Op = iota
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// Src specifies ``src in mask''.
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Src
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)
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var zeroColor image.Color = image.AlphaColor{0}
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// A draw.Image is an image.Image with a Set method to change a single pixel.
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type Image interface {
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image.Image
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Set(x, y int, c image.Color)
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}
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// Draw calls DrawMask with a nil mask.
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func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op) {
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DrawMask(dst, r, src, sp, nil, image.ZP, op)
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}
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// clip clips r against each image's bounds (after translating into the
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// destination image's co-ordinate space) and shifts the points sp and mp by
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// the same amount as the change in r.Min.
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func clip(dst Image, r *image.Rectangle, src image.Image, sp *image.Point, mask image.Image, mp *image.Point) {
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orig := r.Min
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*r = r.Intersect(dst.Bounds())
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*r = r.Intersect(src.Bounds().Add(orig.Sub(*sp)))
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if mask != nil {
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*r = r.Intersect(mask.Bounds().Add(orig.Sub(*mp)))
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}
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dx := r.Min.X - orig.X
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dy := r.Min.Y - orig.Y
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if dx == 0 && dy == 0 {
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return
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}
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(*sp).X += dx
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(*sp).Y += dy
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(*mp).X += dx
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(*mp).Y += dy
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}
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// DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r
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// in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque.
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func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op) {
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clip(dst, &r, src, &sp, mask, &mp)
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if r.Empty() {
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return
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}
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// Fast paths for special cases. If none of them apply, then we fall back to a general but slow implementation.
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if dst0, ok := dst.(*image.RGBA); ok {
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if op == Over {
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if mask == nil {
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switch src0 := src.(type) {
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case *image.ColorImage:
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drawFillOver(dst0, r, src0)
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return
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case *image.RGBA:
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drawCopyOver(dst0, r, src0, sp)
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return
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case *image.NRGBA:
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drawNRGBAOver(dst0, r, src0, sp)
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return
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case *ycbcr.YCbCr:
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drawYCbCr(dst0, r, src0, sp)
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return
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}
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} else if mask0, ok := mask.(*image.Alpha); ok {
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switch src0 := src.(type) {
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case *image.ColorImage:
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drawGlyphOver(dst0, r, src0, mask0, mp)
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return
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}
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}
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} else {
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if mask == nil {
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switch src0 := src.(type) {
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case *image.ColorImage:
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drawFillSrc(dst0, r, src0)
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return
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case *image.RGBA:
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drawCopySrc(dst0, r, src0, sp)
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return
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case *image.NRGBA:
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drawNRGBASrc(dst0, r, src0, sp)
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return
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case *ycbcr.YCbCr:
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drawYCbCr(dst0, r, src0, sp)
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return
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}
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}
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}
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drawRGBA(dst0, r, src, sp, mask, mp, op)
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return
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}
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x0, x1, dx := r.Min.X, r.Max.X, 1
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y0, y1, dy := r.Min.Y, r.Max.Y, 1
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if image.Image(dst) == src && r.Overlaps(r.Add(sp.Sub(r.Min))) {
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// Rectangles overlap: process backward?
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if sp.Y < r.Min.Y || sp.Y == r.Min.Y && sp.X < r.Min.X {
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x0, x1, dx = x1-1, x0-1, -1
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y0, y1, dy = y1-1, y0-1, -1
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}
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}
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var out *image.RGBA64Color
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sy := sp.Y + y0 - r.Min.Y
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my := mp.Y + y0 - r.Min.Y
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for y := y0; y != y1; y, sy, my = y+dy, sy+dy, my+dy {
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sx := sp.X + x0 - r.Min.X
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mx := mp.X + x0 - r.Min.X
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for x := x0; x != x1; x, sx, mx = x+dx, sx+dx, mx+dx {
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ma := uint32(m)
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if mask != nil {
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_, _, _, ma = mask.At(mx, my).RGBA()
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}
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switch {
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case ma == 0:
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if op == Over {
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// No-op.
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} else {
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dst.Set(x, y, zeroColor)
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}
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case ma == m && op == Src:
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dst.Set(x, y, src.At(sx, sy))
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default:
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sr, sg, sb, sa := src.At(sx, sy).RGBA()
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if out == nil {
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out = new(image.RGBA64Color)
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}
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if op == Over {
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dr, dg, db, da := dst.At(x, y).RGBA()
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a := m - (sa * ma / m)
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out.R = uint16((dr*a + sr*ma) / m)
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out.G = uint16((dg*a + sg*ma) / m)
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out.B = uint16((db*a + sb*ma) / m)
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out.A = uint16((da*a + sa*ma) / m)
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} else {
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out.R = uint16(sr * ma / m)
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out.G = uint16(sg * ma / m)
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out.B = uint16(sb * ma / m)
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out.A = uint16(sa * ma / m)
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}
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dst.Set(x, y, out)
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}
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}
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}
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}
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func drawFillOver(dst *image.RGBA, r image.Rectangle, src *image.ColorImage) {
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sr, sg, sb, sa := src.RGBA()
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// The 0x101 is here for the same reason as in drawRGBA.
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a := (m - sa) * 0x101
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i0 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
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i1 := i0 + r.Dx()*4
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for y := r.Min.Y; y != r.Max.Y; y++ {
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for i := i0; i < i1; i += 4 {
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dr := uint32(dst.Pix[i+0])
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dg := uint32(dst.Pix[i+1])
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db := uint32(dst.Pix[i+2])
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da := uint32(dst.Pix[i+3])
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dst.Pix[i+0] = uint8((dr*a/m + sr) >> 8)
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dst.Pix[i+1] = uint8((dg*a/m + sg) >> 8)
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dst.Pix[i+2] = uint8((db*a/m + sb) >> 8)
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dst.Pix[i+3] = uint8((da*a/m + sa) >> 8)
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}
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i0 += dst.Stride
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i1 += dst.Stride
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}
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}
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func drawFillSrc(dst *image.RGBA, r image.Rectangle, src *image.ColorImage) {
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sr, sg, sb, sa := src.RGBA()
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// The built-in copy function is faster than a straightforward for loop to fill the destination with
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// the color, but copy requires a slice source. We therefore use a for loop to fill the first row, and
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// then use the first row as the slice source for the remaining rows.
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i0 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
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i1 := i0 + r.Dx()*4
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for i := i0; i < i1; i += 4 {
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dst.Pix[i+0] = uint8(sr >> 8)
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dst.Pix[i+1] = uint8(sg >> 8)
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dst.Pix[i+2] = uint8(sb >> 8)
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dst.Pix[i+3] = uint8(sa >> 8)
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}
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firstRow := dst.Pix[i0:i1]
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for y := r.Min.Y + 1; y < r.Max.Y; y++ {
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i0 += dst.Stride
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i1 += dst.Stride
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copy(dst.Pix[i0:i1], firstRow)
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}
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}
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func drawCopyOver(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.Point) {
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dx, dy := r.Dx(), r.Dy()
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d0 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
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s0 := (sp.Y-src.Rect.Min.Y)*src.Stride + (sp.X-src.Rect.Min.X)*4
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var (
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ddelta, sdelta int
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i0, i1, idelta int
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)
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if r.Min.Y < sp.Y || r.Min.Y == sp.Y && r.Min.X <= sp.X {
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ddelta = dst.Stride
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sdelta = src.Stride
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i0, i1, idelta = 0, dx*4, +4
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} else {
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// If the source start point is higher than the destination start point, or equal height but to the left,
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// then we compose the rows in right-to-left, bottom-up order instead of left-to-right, top-down.
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d0 += (dy - 1) * dst.Stride
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s0 += (dy - 1) * src.Stride
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ddelta = -dst.Stride
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sdelta = -src.Stride
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i0, i1, idelta = (dx-1)*4, -4, -4
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}
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for ; dy > 0; dy-- {
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dpix := dst.Pix[d0:]
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spix := src.Pix[s0:]
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for i := i0; i != i1; i += idelta {
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sr := uint32(spix[i+0]) * 0x101
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sg := uint32(spix[i+1]) * 0x101
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sb := uint32(spix[i+2]) * 0x101
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sa := uint32(spix[i+3]) * 0x101
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dr := uint32(dpix[i+0])
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dg := uint32(dpix[i+1])
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db := uint32(dpix[i+2])
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da := uint32(dpix[i+3])
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// The 0x101 is here for the same reason as in drawRGBA.
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a := (m - sa) * 0x101
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dpix[i+0] = uint8((dr*a/m + sr) >> 8)
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dpix[i+1] = uint8((dg*a/m + sg) >> 8)
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dpix[i+2] = uint8((db*a/m + sb) >> 8)
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dpix[i+3] = uint8((da*a/m + sa) >> 8)
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}
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d0 += ddelta
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s0 += sdelta
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}
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}
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func drawCopySrc(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.Point) {
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n, dy := 4*r.Dx(), r.Dy()
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d0 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
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s0 := (sp.Y-src.Rect.Min.Y)*src.Stride + (sp.X-src.Rect.Min.X)*4
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var ddelta, sdelta int
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if r.Min.Y <= sp.Y {
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ddelta = dst.Stride
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sdelta = src.Stride
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} else {
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// If the source start point is higher than the destination start point, then we compose the rows
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// in bottom-up order instead of top-down. Unlike the drawCopyOver function, we don't have to
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// check the x co-ordinates because the built-in copy function can handle overlapping slices.
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d0 += (dy - 1) * dst.Stride
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s0 += (dy - 1) * src.Stride
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ddelta = -dst.Stride
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sdelta = -src.Stride
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}
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for ; dy > 0; dy-- {
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copy(dst.Pix[d0:d0+n], src.Pix[s0:s0+n])
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d0 += ddelta
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s0 += sdelta
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}
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}
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func drawNRGBAOver(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image.Point) {
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i0 := (r.Min.X - dst.Rect.Min.X) * 4
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i1 := (r.Max.X - dst.Rect.Min.X) * 4
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si0 := (sp.X - src.Rect.Min.X) * 4
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yMax := r.Max.Y - dst.Rect.Min.Y
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y := r.Min.Y - dst.Rect.Min.Y
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sy := sp.Y - src.Rect.Min.Y
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for ; y != yMax; y, sy = y+1, sy+1 {
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dpix := dst.Pix[y*dst.Stride:]
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spix := src.Pix[sy*src.Stride:]
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for i, si := i0, si0; i < i1; i, si = i+4, si+4 {
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// Convert from non-premultiplied color to pre-multiplied color.
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sa := uint32(spix[si+3]) * 0x101
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sr := uint32(spix[si+0]) * sa / 0xff
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sg := uint32(spix[si+1]) * sa / 0xff
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sb := uint32(spix[si+2]) * sa / 0xff
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dr := uint32(dpix[i+0])
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dg := uint32(dpix[i+1])
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db := uint32(dpix[i+2])
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da := uint32(dpix[i+3])
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// The 0x101 is here for the same reason as in drawRGBA.
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a := (m - sa) * 0x101
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dpix[i+0] = uint8((dr*a/m + sr) >> 8)
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dpix[i+1] = uint8((dg*a/m + sg) >> 8)
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dpix[i+2] = uint8((db*a/m + sb) >> 8)
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dpix[i+3] = uint8((da*a/m + sa) >> 8)
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}
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}
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}
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func drawNRGBASrc(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image.Point) {
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i0 := (r.Min.X - dst.Rect.Min.X) * 4
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i1 := (r.Max.X - dst.Rect.Min.X) * 4
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si0 := (sp.X - src.Rect.Min.X) * 4
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yMax := r.Max.Y - dst.Rect.Min.Y
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y := r.Min.Y - dst.Rect.Min.Y
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sy := sp.Y - src.Rect.Min.Y
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for ; y != yMax; y, sy = y+1, sy+1 {
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dpix := dst.Pix[y*dst.Stride:]
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spix := src.Pix[sy*src.Stride:]
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for i, si := i0, si0; i < i1; i, si = i+4, si+4 {
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// Convert from non-premultiplied color to pre-multiplied color.
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sa := uint32(spix[si+3]) * 0x101
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sr := uint32(spix[si+0]) * sa / 0xff
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sg := uint32(spix[si+1]) * sa / 0xff
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sb := uint32(spix[si+2]) * sa / 0xff
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dpix[i+0] = uint8(sr >> 8)
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dpix[i+1] = uint8(sg >> 8)
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dpix[i+2] = uint8(sb >> 8)
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dpix[i+3] = uint8(sa >> 8)
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}
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}
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}
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func drawYCbCr(dst *image.RGBA, r image.Rectangle, src *ycbcr.YCbCr, sp image.Point) {
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// A YCbCr image is always fully opaque, and so if the mask is implicitly nil
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// (i.e. fully opaque) then the op is effectively always Src.
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var (
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yy, cb, cr uint8
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)
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x0 := (r.Min.X - dst.Rect.Min.X) * 4
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x1 := (r.Max.X - dst.Rect.Min.X) * 4
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y0 := r.Min.Y - dst.Rect.Min.Y
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y1 := r.Max.Y - dst.Rect.Min.Y
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switch src.SubsampleRatio {
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case ycbcr.SubsampleRatio422:
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for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
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dpix := dst.Pix[y*dst.Stride:]
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for x, sx := x0, sp.X; x != x1; x, sx = x+4, sx+1 {
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i := sx / 2
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yy = src.Y[sy*src.YStride+sx]
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cb = src.Cb[sy*src.CStride+i]
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cr = src.Cr[sy*src.CStride+i]
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rr, gg, bb := ycbcr.YCbCrToRGB(yy, cb, cr)
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dpix[x+0] = rr
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dpix[x+1] = gg
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dpix[x+2] = bb
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dpix[x+3] = 255
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}
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}
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case ycbcr.SubsampleRatio420:
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for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
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dpix := dst.Pix[y*dst.Stride:]
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for x, sx := x0, sp.X; x != x1; x, sx = x+4, sx+1 {
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i, j := sx/2, sy/2
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yy = src.Y[sy*src.YStride+sx]
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cb = src.Cb[j*src.CStride+i]
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cr = src.Cr[j*src.CStride+i]
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rr, gg, bb := ycbcr.YCbCrToRGB(yy, cb, cr)
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dpix[x+0] = rr
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dpix[x+1] = gg
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dpix[x+2] = bb
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dpix[x+3] = 255
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}
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}
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default:
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// Default to 4:4:4 subsampling.
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for y, sy := y0, sp.Y; y != y1; y, sy = y+1, sy+1 {
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dpix := dst.Pix[y*dst.Stride:]
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for x, sx := x0, sp.X; x != x1; x, sx = x+4, sx+1 {
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yy = src.Y[sy*src.YStride+sx]
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cb = src.Cb[sy*src.CStride+sx]
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cr = src.Cr[sy*src.CStride+sx]
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rr, gg, bb := ycbcr.YCbCrToRGB(yy, cb, cr)
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dpix[x+0] = rr
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dpix[x+1] = gg
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dpix[x+2] = bb
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dpix[x+3] = 255
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}
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}
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}
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}
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func drawGlyphOver(dst *image.RGBA, r image.Rectangle, src *image.ColorImage, mask *image.Alpha, mp image.Point) {
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i0 := (r.Min.Y-dst.Rect.Min.Y)*dst.Stride + (r.Min.X-dst.Rect.Min.X)*4
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i1 := i0 + r.Dx()*4
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mi0 := (mp.Y-mask.Rect.Min.Y)*mask.Stride + mp.X - mask.Rect.Min.X
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sr, sg, sb, sa := src.RGBA()
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for y, my := r.Min.Y, mp.Y; y != r.Max.Y; y, my = y+1, my+1 {
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for i, mi := i0, mi0; i < i1; i, mi = i+4, mi+1 {
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ma := uint32(mask.Pix[mi])
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if ma == 0 {
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continue
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}
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ma |= ma << 8
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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
|
|
}
|
|
}
|