Commit 6de79ee0 authored by Nigel Tao's avatar Nigel Tao

image: add an Alpha16 type, for completeness.

R=rsc
CC=golang-dev, rog
https://golang.org/cl/1707042
parent d60312c4
......@@ -93,6 +93,16 @@ func (c AlphaColor) RGBA() (r, g, b, a uint32) {
return a, a, a, a
}
// An Alpha16Color represents a 16-bit alpha.
type Alpha16Color struct {
A uint16
}
func (c Alpha16Color) RGBA() (r, g, b, a uint32) {
a = uint32(c.A)
return a, a, a, a
}
// A ColorModel can convert foreign Colors, with a possible loss of precision,
// to a Color from its own color model.
type ColorModel interface {
......@@ -169,6 +179,14 @@ func toAlphaColor(c Color) Color {
return AlphaColor{uint8(a >> 8)}
}
func toAlpha16Color(c Color) Color {
if _, ok := c.(Alpha16Color); ok {
return c
}
_, _, _, a := c.RGBA()
return Alpha16Color{uint16(a)}
}
// The ColorModel associated with RGBAColor.
var RGBAColorModel ColorModel = ColorModelFunc(toRGBAColor)
......@@ -183,3 +201,6 @@ var NRGBA64ColorModel ColorModel = ColorModelFunc(toNRGBA64Color)
// The ColorModel associated with AlphaColor.
var AlphaColorModel ColorModel = ColorModelFunc(toAlphaColor)
// The ColorModel associated with Alpha16Color.
var Alpha16ColorModel ColorModel = ColorModelFunc(toAlpha16Color)
......@@ -255,6 +255,54 @@ func NewAlpha(w, h int) *Alpha {
return &Alpha{pix}
}
// An Alpha16 is an in-memory image backed by a 2-D slice of Alpha16Color values.
type Alpha16 struct {
// The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
Pixel [][]Alpha16Color
}
func (p *Alpha16) ColorModel() ColorModel { return Alpha16ColorModel }
func (p *Alpha16) Width() int {
if len(p.Pixel) == 0 {
return 0
}
return len(p.Pixel[0])
}
func (p *Alpha16) Height() int { return len(p.Pixel) }
func (p *Alpha16) At(x, y int) Color { return p.Pixel[y][x] }
func (p *Alpha16) Set(x, y int, c Color) { p.Pixel[y][x] = toAlpha16Color(c).(Alpha16Color) }
// Opaque scans the entire image and returns whether or not it is fully opaque.
func (p *Alpha16) Opaque() bool {
h := len(p.Pixel)
if h > 0 {
w := len(p.Pixel[0])
for y := 0; y < h; y++ {
pix := p.Pixel[y]
for x := 0; x < w; x++ {
if pix[x].A != 0xffff {
return false
}
}
}
}
return true
}
// NewAlpha16 returns a new Alpha16 with the given width and height.
func NewAlpha16(w, h int) *Alpha16 {
buf := make([]Alpha16Color, w*h)
pix := make([][]Alpha16Color, h)
for y := range pix {
pix[y] = buf[w*y : w*(y+1)]
}
return &Alpha16{pix}
}
// A PalettedColorModel represents a fixed palette of colors.
type PalettedColorModel []Color
......
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