1 files changed, 121 insertions, 0 deletions
diff --git a/src/image/color/palette/gen.go b/src/image/color/palette/gen.go
new file mode 100644
index 000000000..2b5fdaaf2
--- /dev/null
+++ b/src/image/color/palette/gen.go
@@ -0,0 +1,121 @@
+// Copyright 2013 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.
+
+// +build ignore
+
+package main
+
+// This program generates palette.go. Invoke it as
+//	go run gen.go -output palette.go
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/format"
+	"io"
+	"io/ioutil"
+	"log"
+)
+
+var filename = flag.String("output", "palette.go", "output file name")
+
+func main() {
+	flag.Parse()
+
+	var buf bytes.Buffer
+
+	fmt.Fprintln(&buf, `// Copyright 2013 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.`)
+	fmt.Fprintln(&buf)
+	fmt.Fprintln(&buf, "// generated by go run gen.go -output palette.go; DO NOT EDIT")
+	fmt.Fprintln(&buf)
+	fmt.Fprintln(&buf, "package palette")
+	fmt.Fprintln(&buf)
+	fmt.Fprintln(&buf, `import "image/color"`)
+	fmt.Fprintln(&buf)
+	printPlan9(&buf)
+	printWebSafe(&buf)
+
+	data, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = ioutil.WriteFile(*filename, data, 0644)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func printPlan9(w io.Writer) {
+	c, lines := [3]int{}, [256]string{}
+	for r, i := 0, 0; r != 4; r++ {
+		for v := 0; v != 4; v, i = v+1, i+16 {
+			for g, j := 0, v-r; g != 4; g++ {
+				for b := 0; b != 4; b, j = b+1, j+1 {
+					den := r
+					if g > den {
+						den = g
+					}
+					if b > den {
+						den = b
+					}
+					if den == 0 {
+						c[0] = 0x11 * v
+						c[1] = 0x11 * v
+						c[2] = 0x11 * v
+					} else {
+						num := 17 * (4*den + v)
+						c[0] = r * num / den
+						c[1] = g * num / den
+						c[2] = b * num / den
+					}
+					lines[i+(j&0x0f)] =
+						fmt.Sprintf("\tcolor.RGBA{0x%02x, 0x%02x, 0x%02x, 0xff},", c[0], c[1], c[2])
+				}
+			}
+		}
+	}
+	fmt.Fprintln(w, "// Plan9 is a 256-color palette that partitions the 24-bit RGB space")
+	fmt.Fprintln(w, "// into 4×4×4 subdivision, with 4 shades in each subcube. Compared to the")
+	fmt.Fprintln(w, "// WebSafe, the idea is to reduce the color resolution by dicing the")
+	fmt.Fprintln(w, "// color cube into fewer cells, and to use the extra space to increase the")
+	fmt.Fprintln(w, "// intensity resolution. This results in 16 gray shades (4 gray subcubes with")
+	fmt.Fprintln(w, "// 4 samples in each), 13 shades of each primary and secondary color (3")
+	fmt.Fprintln(w, "// subcubes with 4 samples plus black) and a reasonable selection of colors")
+	fmt.Fprintln(w, "// covering the rest of the color cube. The advantage is better representation")
+	fmt.Fprintln(w, "// of continuous tones.")
+	fmt.Fprintln(w, "//")
+	fmt.Fprintln(w, "// This palette was used in the Plan 9 Operating System, described at")
+	fmt.Fprintln(w, "// http://plan9.bell-labs.com/magic/man2html/6/color")
+	fmt.Fprintln(w, "var Plan9 = []color.Color{")
+	for _, line := range lines {
+		fmt.Fprintln(w, line)
+	}
+	fmt.Fprintln(w, "}")
+	fmt.Fprintln(w)
+}
+
+func printWebSafe(w io.Writer) {
+	lines := [6 * 6 * 6]string{}
+	for r := 0; r < 6; r++ {
+		for g := 0; g < 6; g++ {
+			for b := 0; b < 6; b++ {
+				lines[36*r+6*g+b] =
+					fmt.Sprintf("\tcolor.RGBA{0x%02x, 0x%02x, 0x%02x, 0xff},", 0x33*r, 0x33*g, 0x33*b)
+			}
+		}
+	}
+	fmt.Fprintln(w, "// WebSafe is a 216-color palette that was popularized by early versions")
+	fmt.Fprintln(w, "// of Netscape Navigator. It is also known as the Netscape Color Cube.")
+	fmt.Fprintln(w, "//")
+	fmt.Fprintln(w, "// See http://en.wikipedia.org/wiki/Web_colors#Web-safe_colors for details.")
+	fmt.Fprintln(w, "var WebSafe = []color.Color{")
+	for _, line := range lines {
+		fmt.Fprintln(w, line)
+	}
+	fmt.Fprintln(w, "}")
+	fmt.Fprintln(w)
+}