1 files changed, 117 insertions, 0 deletions
diff --git a/src/pkg/exp/draw/color.go b/src/pkg/exp/draw/color.go
new file mode 100644
index 000000000..bae35eba5
--- /dev/null
+++ b/src/pkg/exp/draw/color.go
@@ -0,0 +1,117 @@
+// 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.
+
+package draw
+
+import "image"
+
+// A Color represents a color with 8-bit R, G, B, and A values,
+// packed into a uint32—0xRRGGBBAA—so that comparison
+// is defined on colors.
+// Color implements image.Color.
+// Color also implements image.Image: it is a
+// 10⁹x10⁹-pixel image of uniform color.
+type Color uint32
+
+// Check that Color implements image.Color and image.Image
+var _ image.Color = Black
+var _ image.Image = Black
+
+var (
+	Opaque Color = 0xFFFFFFFF;
+	Transparent Color = 0x00000000;
+	Black Color = 0x000000FF;
+	White Color = 0xFFFFFFFF;
+	Red Color = 0xFF0000FF;
+	Green Color = 0x00FF00FF;
+	Blue Color = 0x0000FFFF;
+	Cyan Color = 0x00FFFFFF;
+	Magenta Color = 0xFF00FFFF;
+	Yellow Color = 0xFFFF00FF;
+	PaleYellow Color = 0xFFFFAAFF;
+	DarkYellow Color = 0xEEEE9EFF;
+	DarkGreen Color = 0x448844FF;
+	PaleGreen Color = 0xAAFFAAFF;
+	MedGreen Color = 0x88CC88FF;
+	DarkBlue Color = 0x000055FF;
+	PaleBlueGreen Color = 0xAAFFFFFF;
+	PaleBlue Color = 0x0000BBFF;
+	BlueGreen Color = 0x008888FF;
+	GreyGreen Color = 0x55AAAAFF;
+	PaleGreyGreen Color = 0x9EEEEEFF;
+	YellowGreen Color = 0x99994CFF;
+	MedBlue Color = 0x000099FF;
+	GreyBlue Color = 0x005DBBFF;
+	PaleGreyBlue Color = 0x4993DDFF;
+	PurpleBlue Color = 0x8888CCFF;
+)
+
+func (c Color) RGBA() (r, g, b, a uint32) {
+	x := uint32(c);
+	r, g, b, a = x>>24, (x>>16)&0xFF, (x>>8)&0xFF, x&0xFF;
+	r |= r<<8;
+	r |= r<<16;
+	g |= g<<8;
+	g |= g<<16;
+	b |= b<<8;
+	b |= b<<16;
+	a |= a<<8;
+	a |= a<<16;
+	return;
+}
+
+// SetAlpha returns the color obtained by changing
+// c's alpha value to a and scaling r, g, and b appropriately.
+func (c Color) SetAlpha(a uint8) Color {
+	r, g, b, oa := c>>24, (c>>16)&0xFF, (c>>8)&0xFF, c&0xFF;
+	if oa == 0 {
+		return 0
+	}
+	r = r*Color(a)/oa;
+	if r < 0 {
+		r = 0;
+	}
+	if r > 0xFF {
+		r = 0xFF;
+	}
+	g = g*Color(a)/oa;
+	if g < 0 {
+		g = 0;
+	}
+	if g > 0xFF {
+		g = 0xFF;
+	}
+	b = b*Color(a)/oa;
+	if b < 0 {
+		b = 0;
+	}
+	if b > 0xFF {
+		b = 0xFF;
+	}
+	return r<<24 | g<<16 | b<<8 | Color(a);
+}
+
+func (c Color) Width() int {
+	return 1e9;
+}
+
+func (c Color) Height() int {
+	return 1e9;
+}
+
+func (c Color) At(x, y int) image.Color {
+	return c;
+}
+
+func toColor(color image.Color) image.Color {
+	if c, ok := color.(Color); ok {
+		return c;
+	}
+	r, g, b, a := color.RGBA();
+	return Color(r>>24<<24 | g>>24<<16 | b>>24<<8 | a>>24);
+}
+
+func (c Color) ColorModel() image.ColorModel {
+	return image.ColorModelFunc(toColor);
+}