mirror of
https://github.com/golang/go
synced 2024-11-22 03:44:39 -07:00
Make image.Color.RGBA return 16 bit color instead of 32 bit color.
R=rsc CC=golang-dev https://golang.org/cl/1388041
This commit is contained in:
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d5a8647d80
commit
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@ -51,13 +51,9 @@ func (c Color) RGBA() (r, g, b, a uint32) {
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x := uint32(c)
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r, g, b, a = x>>24, (x>>16)&0xFF, (x>>8)&0xFF, x&0xFF
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r |= r << 8
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r |= r << 16
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g |= g << 8
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g |= g << 16
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b |= b << 8
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b |= b << 16
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a |= a << 8
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a |= a << 16
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return
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}
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@ -103,7 +99,7 @@ func toColor(color image.Color) image.Color {
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return c
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}
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r, g, b, a := color.RGBA()
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return Color(r>>24<<24 | g>>24<<16 | b>>24<<8 | a>>24)
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return Color(r>>8<<24 | g>>8<<16 | b>>8<<8 | a>>8)
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}
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func (c Color) ColorModel() image.ColorModel { return image.ColorModelFunc(toColor) }
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@ -105,13 +105,10 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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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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// A nil mask is equivalent to a fully opaque, infinitely large mask.
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// We work in 16-bit color, so that multiplying two values does not overflow a uint32.
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const M = 1<<16 - 1
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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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ma >>= 16
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}
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switch {
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case ma == 0:
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@ -124,19 +121,11 @@ func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Imag
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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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sr >>= 16
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sg >>= 16
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sb >>= 16
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sa >>= 16
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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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dr >>= 16
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dg >>= 16
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db >>= 16
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da >>= 16
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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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@ -158,10 +147,6 @@ func drawGlyphOver(dst *image.RGBA, r Rectangle, src image.ColorImage, mask *ima
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x0, x1 := r.Min.X, r.Max.X
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y0, y1 := r.Min.Y, r.Max.Y
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cr, cg, cb, ca := src.RGBA()
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cr >>= 16
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cg >>= 16
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cb >>= 16
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ca >>= 16
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for y, my := y0, mp.Y; y != y1; y, my = y+1, my+1 {
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p := dst.Pixel[y]
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for x, mx := x0, mp.X; x != x1; x, mx = x+1, mx+1 {
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@ -192,7 +177,7 @@ func drawFill(dst *image.RGBA, r Rectangle, src image.ColorImage) {
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return
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}
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cr, cg, cb, ca := src.RGBA()
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color := image.RGBAColor{uint8(cr >> 24), uint8(cg >> 24), uint8(cb >> 24), uint8(ca >> 24)}
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color := image.RGBAColor{uint8(cr >> 8), uint8(cg >> 8), uint8(cb >> 8), uint8(ca >> 8)}
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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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@ -238,13 +223,8 @@ func drawRGBA(dst *image.RGBA, r Rectangle, src image.Image, sp Point, mask imag
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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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ma >>= 16
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}
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sr, sg, sb, sa := src.At(sx, sy).RGBA()
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sr >>= 16
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sg >>= 16
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sb >>= 16
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sa >>= 16
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var dr, dg, db, da uint32
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if op == Over {
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rgba := p[x]
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@ -106,20 +106,11 @@ func makeGolden(dst image.Image, t drawTest) image.Image {
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var dr, dg, db, da uint32
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if t.op == Over {
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dr, dg, db, da = dst.At(x, y).RGBA()
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dr >>= 16
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dg >>= 16
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db >>= 16
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da >>= 16
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}
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sr, sg, sb, sa := t.src.At(sx, sy).RGBA()
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sr >>= 16
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sg >>= 16
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sb >>= 16
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sa >>= 16
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ma := uint32(M)
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if t.mask != nil {
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_, _, _, ma = t.mask.At(mx, my).RGBA()
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ma >>= 16
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}
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a := M - (sa * ma / M)
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golden.Set(x, y, image.RGBA64Color{
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@ -61,16 +61,12 @@ func (p Color) RGBA() (r, g, b, a uint32) {
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x := uint32(p)
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a = x >> 24
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a |= a << 8
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a |= a << 16
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r = (x >> 16) & 0xFF
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r |= r << 8
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r |= r << 16
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g = (x >> 8) & 0xFF
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g |= g << 8
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g |= g << 16
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b = x & 0xFF
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b |= b << 8
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b |= b << 16
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return
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}
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@ -4,14 +4,15 @@
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package image
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// TODO(nigeltao): Think about how floating-point color models work.
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// All Colors can convert themselves, with a possible loss of precision, to 128-bit alpha-premultiplied RGBA.
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// All Colors can convert themselves, with a possible loss of precision,
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// to 64-bit alpha-premultiplied RGBA. Each channel value ranges within
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// [0, 0xFFFF].
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type Color interface {
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RGBA() (r, g, b, a uint32)
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}
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// An RGBAColor represents a traditional 32-bit alpha-premultiplied color, having 8 bits for each of red, green, blue and alpha.
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// An RGBAColor represents a traditional 32-bit alpha-premultiplied color,
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// having 8 bits for each of red, green, blue and alpha.
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type RGBAColor struct {
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R, G, B, A uint8
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}
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@ -19,34 +20,23 @@ type RGBAColor struct {
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func (c RGBAColor) RGBA() (r, g, b, a uint32) {
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r = uint32(c.R)
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r |= r << 8
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r |= r << 16
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g = uint32(c.G)
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g |= g << 8
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g |= g << 16
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b = uint32(c.B)
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b |= b << 8
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b |= b << 16
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a = uint32(c.A)
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a |= a << 8
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a |= a << 16
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return
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}
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// An RGBA64Color represents a 64-bit alpha-premultiplied color, having 16 bits for each of red, green, blue and alpha.
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// An RGBA64Color represents a 64-bit alpha-premultiplied color,
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// having 16 bits for each of red, green, blue and alpha.
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type RGBA64Color struct {
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R, G, B, A uint16
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}
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func (c RGBA64Color) RGBA() (r, g, b, a uint32) {
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r = uint32(c.R)
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r |= r << 16
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g = uint32(c.G)
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g |= g << 16
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b = uint32(c.B)
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b |= b << 16
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a = uint32(c.A)
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a |= a << 16
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return
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return uint32(c.R), uint32(c.G), uint32(c.B), uint32(c.A)
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}
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// An NRGBAColor represents a non-alpha-premultiplied 32-bit color.
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@ -59,24 +49,21 @@ func (c NRGBAColor) RGBA() (r, g, b, a uint32) {
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r |= r << 8
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r *= uint32(c.A)
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r /= 0xff
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r |= r << 16
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g = uint32(c.G)
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g |= g << 8
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g *= uint32(c.A)
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g /= 0xff
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g |= g << 16
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b = uint32(c.B)
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b |= b << 8
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b *= uint32(c.A)
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b /= 0xff
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b |= b << 16
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a = uint32(c.A)
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a |= a << 8
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a |= a << 16
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return
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}
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// An NRGBA64Color represents a non-alpha-premultiplied 64-bit color, having 16 bits for each of red, green, blue and alpha.
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// An NRGBA64Color represents a non-alpha-premultiplied 64-bit color,
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// having 16 bits for each of red, green, blue and alpha.
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type NRGBA64Color struct {
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R, G, B, A uint16
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}
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@ -85,18 +72,13 @@ func (c NRGBA64Color) RGBA() (r, g, b, a uint32) {
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r = uint32(c.R)
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r *= uint32(c.A)
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r /= 0xffff
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r |= r << 16
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g = uint32(c.G)
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g *= uint32(c.A)
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g /= 0xffff
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g |= g << 16
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b = uint32(c.B)
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b *= uint32(c.A)
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b /= 0xffff
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b |= b << 16
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a = uint32(c.A)
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a |= a << 8
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a |= a << 16
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return
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}
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@ -108,12 +90,11 @@ type AlphaColor struct {
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func (c AlphaColor) RGBA() (r, g, b, a uint32) {
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a = uint32(c.A)
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a |= a << 8
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a |= a << 16
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return a, a, a, a
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}
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// A ColorModel can convert foreign Colors, with a possible loss of precision, to a Color
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// from its own color model.
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// A ColorModel can convert foreign Colors, with a possible loss of precision,
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// to a Color from its own color model.
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type ColorModel interface {
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Convert(c Color) Color
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}
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@ -129,36 +110,32 @@ func (f ColorModelFunc) Convert(c Color) Color {
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}
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func toRGBAColor(c Color) Color {
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if _, ok := c.(RGBAColor); ok { // no-op conversion
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if _, ok := c.(RGBAColor); ok {
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return c
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}
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r, g, b, a := c.RGBA()
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return RGBAColor{uint8(r >> 24), uint8(g >> 24), uint8(b >> 24), uint8(a >> 24)}
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return RGBAColor{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
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}
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func toRGBA64Color(c Color) Color {
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if _, ok := c.(RGBA64Color); ok { // no-op conversion
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if _, ok := c.(RGBA64Color); ok {
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return c
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}
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r, g, b, a := c.RGBA()
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return RGBA64Color{uint16(r >> 16), uint16(g >> 16), uint16(b >> 16), uint16(a >> 16)}
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return RGBA64Color{uint16(r), uint16(g), uint16(b), uint16(a)}
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}
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func toNRGBAColor(c Color) Color {
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if _, ok := c.(NRGBAColor); ok { // no-op conversion
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if _, ok := c.(NRGBAColor); ok {
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return c
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}
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r, g, b, a := c.RGBA()
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a >>= 16
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if a == 0xffff {
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return NRGBAColor{uint8(r >> 24), uint8(g >> 24), uint8(b >> 24), 0xff}
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return NRGBAColor{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), 0xff}
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}
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if a == 0 {
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return NRGBAColor{0, 0, 0, 0}
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}
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r >>= 16
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g >>= 16
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b >>= 16
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// Since Color.RGBA returns a alpha-premultiplied color, we should have r <= a && g <= a && b <= a.
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r = (r * 0xffff) / a
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g = (g * 0xffff) / a
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@ -167,14 +144,10 @@ func toNRGBAColor(c Color) Color {
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}
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func toNRGBA64Color(c Color) Color {
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if _, ok := c.(NRGBA64Color); ok { // no-op conversion
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if _, ok := c.(NRGBA64Color); ok {
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return c
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}
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r, g, b, a := c.RGBA()
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a >>= 16
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r >>= 16
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g >>= 16
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b >>= 16
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if a == 0xffff {
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return NRGBA64Color{uint16(r), uint16(g), uint16(b), 0xffff}
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}
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@ -189,11 +162,11 @@ func toNRGBA64Color(c Color) Color {
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}
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func toAlphaColor(c Color) Color {
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if _, ok := c.(AlphaColor); ok { // no-op conversion
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if _, ok := c.(AlphaColor); ok {
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return c
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}
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_, _, _, a := c.RGBA()
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return AlphaColor{uint8(a >> 24)}
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return AlphaColor{uint8(a >> 8)}
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}
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// The ColorModel associated with RGBAColor.
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@ -185,21 +185,18 @@ func (p PalettedColorModel) Convert(c Color) Color {
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if len(p) == 0 {
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return nil
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}
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// TODO(nigeltao): Revisit the "pick the palette color which minimizes sum-squared-difference"
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// algorithm when the premultiplied vs unpremultiplied issue is resolved.
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// Currently, we only compare the R, G and B values, and ignore A.
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cr, cg, cb, _ := c.RGBA()
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// Shift by 17 bits to avoid potential uint32 overflow in sum-squared-difference.
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cr >>= 17
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cg >>= 17
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cb >>= 17
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// Shift by 1 bit to avoid potential uint32 overflow in sum-squared-difference.
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cr >>= 1
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cg >>= 1
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cb >>= 1
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result := Color(nil)
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bestSSD := uint32(1<<32 - 1)
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for _, v := range p {
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vr, vg, vb, _ := v.RGBA()
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vr >>= 17
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vg >>= 17
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vb >>= 17
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vr >>= 1
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vg >>= 1
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vb >>= 1
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dr, dg, db := diff(cr, vr), diff(cg, vg), diff(cb, vb)
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ssd := (dr * dr) + (dg * dg) + (db * db)
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if ssd < bestSSD {
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@ -76,9 +76,9 @@ func sng(w io.WriteCloser, filename string, png image.Image) {
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io.WriteString(w, "PLTE {\n")
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for i := 0; i < len(cpm); i++ {
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r, g, b, _ := cpm[i].RGBA()
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r >>= 24
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g >>= 24
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b >>= 24
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r >>= 8
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g >>= 8
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b >>= 8
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fmt.Fprintf(w, " (%3d,%3d,%3d) # rgb = (0x%02x,0x%02x,0x%02x)\n", r, g, b, r, g, b)
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}
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io.WriteString(w, "}\n")
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@ -37,7 +37,7 @@ func opaque(m image.Image) bool {
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for y := 0; y < m.Height(); y++ {
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for x := 0; x < m.Width(); x++ {
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_, _, _, a := m.At(x, y).RGBA()
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if a != 0xffffffff {
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if a != 0xffff {
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return false
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}
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}
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@ -101,13 +101,13 @@ func (e *encoder) writePLTE(p image.PalettedColorModel) {
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}
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for i := 0; i < len(p); i++ {
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r, g, b, a := p[i].RGBA()
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if a != 0xffffffff {
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if a != 0xffff {
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e.err = UnsupportedError("non-opaque palette color")
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return
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}
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e.tmp[3*i+0] = uint8(r >> 24)
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e.tmp[3*i+1] = uint8(g >> 24)
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e.tmp[3*i+2] = uint8(b >> 24)
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e.tmp[3*i+0] = uint8(r >> 8)
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e.tmp[3*i+1] = uint8(g >> 8)
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e.tmp[3*i+2] = uint8(b >> 8)
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}
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e.writeChunk(e.tmp[0:3*len(p)], "PLTE")
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}
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@ -261,9 +261,9 @@ func writeImage(w io.Writer, m image.Image, ct uint8) os.Error {
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for x := 0; x < m.Width(); x++ {
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// We have previously verified that the alpha value is fully opaque.
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r, g, b, _ := m.At(x, y).RGBA()
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cr[0][3*x+1] = uint8(r >> 24)
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cr[0][3*x+2] = uint8(g >> 24)
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cr[0][3*x+3] = uint8(b >> 24)
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cr[0][3*x+1] = uint8(r >> 8)
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cr[0][3*x+2] = uint8(g >> 8)
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cr[0][3*x+3] = uint8(b >> 8)
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}
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case ctPaletted:
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for x := 0; x < m.Width(); x++ {
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