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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.
// The image package implements a basic 2-D image library.
package image
// An Image is a rectangular grid of Colors drawn from a ColorModel.
type Image interface {
ColorModel() ColorModel;
Width() int;
Height() int;
// At(0, 0) returns the upper-left pixel of the grid.
// At(Width()-1, Height()-1) returns the lower-right pixel.
At(x, y int) Color;
}
// An RGBA is an in-memory image backed by a 2-D slice of RGBAColor values.
type RGBA struct {
// The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
Pixel [][]RGBAColor;
}
func (p *RGBA) ColorModel() ColorModel { return RGBAColorModel }
func (p *RGBA) Width() int {
if len(p.Pixel) == 0 {
return 0;
}
return len(p.Pixel[0]);
}
func (p *RGBA) Height() int { return len(p.Pixel) }
func (p *RGBA) At(x, y int) Color { return p.Pixel[y][x] }
func (p *RGBA) Set(x, y int, c Color) { p.Pixel[y][x] = toRGBAColor(c).(RGBAColor) }
// NewRGBA returns a new RGBA with the given width and height.
func NewRGBA(w, h int) *RGBA {
pixel := make([][]RGBAColor, h);
for y := 0; y < int(h); y++ {
pixel[y] = make([]RGBAColor, w);
}
return &RGBA{pixel};
}
// An RGBA64 is an in-memory image backed by a 2-D slice of RGBA64Color values.
type RGBA64 struct {
// The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
Pixel [][]RGBA64Color;
}
func (p *RGBA64) ColorModel() ColorModel { return RGBA64ColorModel }
func (p *RGBA64) Width() int {
if len(p.Pixel) == 0 {
return 0;
}
return len(p.Pixel[0]);
}
func (p *RGBA64) Height() int { return len(p.Pixel) }
func (p *RGBA64) At(x, y int) Color { return p.Pixel[y][x] }
func (p *RGBA64) Set(x, y int, c Color) { p.Pixel[y][x] = toRGBA64Color(c).(RGBA64Color) }
// NewRGBA64 returns a new RGBA64 with the given width and height.
func NewRGBA64(w, h int) *RGBA64 {
pixel := make([][]RGBA64Color, h);
for y := 0; y < int(h); y++ {
pixel[y] = make([]RGBA64Color, w);
}
return &RGBA64{pixel};
}
// A NRGBA is an in-memory image backed by a 2-D slice of NRGBAColor values.
type NRGBA struct {
// The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
Pixel [][]NRGBAColor;
}
func (p *NRGBA) ColorModel() ColorModel { return NRGBAColorModel }
func (p *NRGBA) Width() int {
if len(p.Pixel) == 0 {
return 0;
}
return len(p.Pixel[0]);
}
func (p *NRGBA) Height() int { return len(p.Pixel) }
func (p *NRGBA) At(x, y int) Color { return p.Pixel[y][x] }
func (p *NRGBA) Set(x, y int, c Color) { p.Pixel[y][x] = toNRGBAColor(c).(NRGBAColor) }
// NewNRGBA returns a new NRGBA with the given width and height.
func NewNRGBA(w, h int) *NRGBA {
pixel := make([][]NRGBAColor, h);
for y := 0; y < int(h); y++ {
pixel[y] = make([]NRGBAColor, w);
}
return &NRGBA{pixel};
}
// A NRGBA64 is an in-memory image backed by a 2-D slice of NRGBA64Color values.
type NRGBA64 struct {
// The Pixel field's indices are y first, then x, so that At(x, y) == Pixel[y][x].
Pixel [][]NRGBA64Color;
}
func (p *NRGBA64) ColorModel() ColorModel { return NRGBA64ColorModel }
func (p *NRGBA64) Width() int {
if len(p.Pixel) == 0 {
return 0;
}
return len(p.Pixel[0]);
}
func (p *NRGBA64) Height() int { return len(p.Pixel) }
func (p *NRGBA64) At(x, y int) Color { return p.Pixel[y][x] }
func (p *NRGBA64) Set(x, y int, c Color) { p.Pixel[y][x] = toNRGBA64Color(c).(NRGBA64Color) }
// NewNRGBA64 returns a new NRGBA64 with the given width and height.
func NewNRGBA64(w, h int) *NRGBA64 {
pixel := make([][]NRGBA64Color, h);
for y := 0; y < int(h); y++ {
pixel[y] = make([]NRGBA64Color, w);
}
return &NRGBA64{pixel};
}
// A PalettedColorModel represents a fixed palette of colors.
type PalettedColorModel []Color
func diff(a, b uint32) uint32 {
if a > b {
return a-b;
}
return b-a;
}
// Convert returns the palette color closest to c in Euclidean R,G,B space.
func (p PalettedColorModel) Convert(c Color) Color {
if len(p) == 0 {
return nil;
}
// TODO(nigeltao): Revisit the "pick the palette color which minimizes sum-squared-difference"
// algorithm when the premultiplied vs unpremultiplied issue is resolved.
// Currently, we only compare the R, G and B values, and ignore A.
cr, cg, cb, _ := c.RGBA();
// Shift by 17 bits to avoid potential uint32 overflow in sum-squared-difference.
cr >>= 17;
cg >>= 17;
cb >>= 17;
result := Color(nil);
bestSSD := uint32(1<<32 - 1);
for _, v := range p {
vr, vg, vb, _ := v.RGBA();
vr >>= 17;
vg >>= 17;
vb >>= 17;
dr, dg, db := diff(cr, vr), diff(cg, vg), diff(cb, vb);
ssd := (dr*dr)+(dg*dg)+(db*db);
if ssd < bestSSD {
bestSSD = ssd;
result = v;
}
}
return result;
}
// A Paletted is an in-memory image backed by a 2-D slice of uint8 values and a PalettedColorModel.
type Paletted struct {
// The Pixel field's indices are y first, then x, so that At(x, y) == Palette[Pixel[y][x]].
Pixel [][]uint8;
Palette PalettedColorModel;
}
func (p *Paletted) ColorModel() ColorModel { return p.Palette }
func (p *Paletted) Width() int {
if len(p.Pixel) == 0 {
return 0;
}
return len(p.Pixel[0]);
}
func (p *Paletted) Height() int { return len(p.Pixel) }
func (p *Paletted) At(x, y int) Color { return p.Palette[p.Pixel[y][x]] }
func (p *Paletted) ColorIndexAt(x, y int) uint8 {
return p.Pixel[y][x];
}
func (p *Paletted) SetColorIndex(x, y int, index uint8) {
p.Pixel[y][x] = index;
}
// NewPaletted returns a new Paletted with the given width, height and palette.
func NewPaletted(w, h int, m PalettedColorModel) *Paletted {
pixel := make([][]uint8, h);
for y := 0; y < int(h); y++ {
pixel[y] = make([]uint8, w);
}
return &Paletted{pixel, m};
}
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