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// // 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.
// //go: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"
// "log"
// "os"
// )
// 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, "// Code 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 = os.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, "// https://9p.io/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 https://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)
// }