1 files changed, 140 insertions, 0 deletions
diff --git a/src/pkg/image/image.go b/src/pkg/image/image.go
new file mode 100644
index 000000000..f63df1bd3
--- /dev/null
+++ b/src/pkg/image/image.go
@@ -0,0 +1,140 @@
+// 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);
+}
+
+// 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);
+}
+
+// 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, ca := 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, va := 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 byte 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 [][]byte;
+	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]];
+}