| // 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 | gofmt > palette.go |
| |
| import ( |
| "fmt" |
| ) |
| |
| func main() { |
| fmt.Println("// generated by go run gen.go; DO NOT EDIT") |
| fmt.Println() |
| fmt.Println("// Package palette provides standard color palettes.") |
| fmt.Println("package palette") |
| fmt.Println() |
| fmt.Println(`import "image/color"`) |
| fmt.Println() |
| printPlan9() |
| printWebSafe() |
| } |
| |
| func printPlan9() { |
| 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.Println("// Plan9 is a 256-color palette that partitions the 24-bit RGB space") |
| fmt.Println("// into 4×4×4 subdivision, with 4 shades in each subcube. Compared to the") |
| fmt.Println("// WebSafe, the idea is to reduce the color resolution by dicing the") |
| fmt.Println("// color cube into fewer cells, and to use the extra space to increase the") |
| fmt.Println("// intensity resolution. This results in 16 gray shades (4 gray subcubes with") |
| fmt.Println("// 4 samples in each), 13 shades of each primary and secondary color (3") |
| fmt.Println("// subcubes with 4 samples plus black) and a reasonable selection of colors") |
| fmt.Println("// covering the rest of the color cube. The advantage is better representation") |
| fmt.Println("// of continuous tones.") |
| fmt.Println("//") |
| fmt.Println("// This palette was used in the Plan 9 Operating System, described at") |
| fmt.Println("// http://plan9.bell-labs.com/magic/man2html/6/color") |
| fmt.Println("var Plan9 = []color.Color{") |
| for _, line := range lines { |
| fmt.Println(line) |
| } |
| fmt.Println("}") |
| fmt.Println() |
| } |
| |
| func printWebSafe() { |
| 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.Println("// WebSafe is a 216-color palette that was popularized by early versions") |
| fmt.Println("// of Netscape Navigator. It is also known as the Netscape Color Cube.") |
| fmt.Println("//") |
| fmt.Println("// See http://en.wikipedia.org/wiki/Web_colors#Web-safe_colors for details.") |
| fmt.Println("var WebSafe = []color.Color{") |
| for _, line := range lines { |
| fmt.Println(line) |
| } |
| fmt.Println("}") |
| fmt.Println() |
| } |