clean up command-line parsing and add some error-diffusion experiments
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94d1e465c9
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301ee00b69
@ -69,3 +69,52 @@ func colorBayer(level int, p color.Palette) quantizerFunction {
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return p[p.Index(rc)]
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}
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}
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func colorError(errMap map[coord]float64, d diffusion, palette color.Palette) quantizerFunction {
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r := float64(len(palette))
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return func(x int, y int, c color.Color) color.Color {
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p := coord{x: x, y: y}
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rc := permuteColor(c, uint8(r*errMap[p]))
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delete(errMap, p) // don't let the error map grow too big
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nc := palette[palette.Index(rc)]
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l := luminence(c) - luminence(nc)
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applyError(d, l, p, errMap)
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return nc
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}
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}
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func simpleColorErrorDiffusion() quantizerFunction {
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errMap := make(map[coord]float64)
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d := diffusion{
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divisor: 2.0,
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matrix: map[coord]float64{
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{x: 1, y: 0}: 1.0,
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{x: 0, y: 1}: 1.0,
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},
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}
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return colorError(errMap, d, sixteencolors)
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}
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func colorJarvisJudiceNinke() quantizerFunction {
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errMap := make(map[coord]float64)
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d := diffusion{
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divisor: 48.0,
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matrix: map[coord]float64{
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{x: 1, y: 0}: 7.0,
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{x: 2, y: 0}: 5.0,
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{x: -2, y: 1}: 3.0,
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{x: -1, y: 1}: 5.0,
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{x: 0, y: 1}: 7.0,
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{x: 1, y: 1}: 5.0,
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{x: 2, y: 1}: 3.0,
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{x: -2, y: 2}: 1.0,
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{x: -1, y: 2}: 3.0,
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{x: 0, y: 2}: 5.0,
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{x: 1, y: 2}: 3.0,
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{x: 2, y: 2}: 1.0,
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},
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}
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return colorError(errMap, d, sixteencolors)
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}
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141
main.go
141
main.go
@ -1,6 +1,7 @@
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package main
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import (
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"flag"
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"fmt"
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"image"
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"image/color"
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@ -32,25 +33,73 @@ func apply(i image.Image, f quantizerFunction) image.Image {
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return out
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}
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type ditherOpts struct {
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raw string
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level int
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invert bool
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}
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func (o *ditherOpts) Set(input string) error {
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for _, p := range input {
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switch p {
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case 'n':
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o.invert = true
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case '0':
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o.level = 0
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case '1':
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o.level = 1
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default:
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return fmt.Errorf("unknown option %s", string(p))
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}
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}
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return nil
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}
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func (o *ditherOpts) String() string {
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return o.raw
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}
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func main() {
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if len(os.Args) == 1 || len(os.Args) > 4 || os.Args[1] == "help" {
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fmt.Printf(`usage: %s <path/to/image.ext> <dither_option> <path/to/output.png>
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Supported dither options are: noop; naive; randomnoise; bayer{0,1}; bayer{0,1}n
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Supported input image formats are jpg, png
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`, os.Args[0])
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ditherOpts := &ditherOpts{}
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filenameFlag := flag.String("in", "", "Input filename. PNG or JPG formats accepted.")
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verboseFlag := flag.Bool("v", false, "Include diagnostic log lines.")
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paletteFlag := flag.String("p", "bw",
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`Palette to use. Defaults to 'bw': black-and-white.
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Pass 'sixteen' for the classic sixteen-color palette.
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Not all dither options support palettes; unsupported ditherers will ignore this flag.`)
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dithererFlag := flag.String("d", "naive",
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`Ditherer to use. Defaults to 'naive', which just flattens to nearest color.
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Other options: 'noise', 'bayer', 'error', 'floydsteinberg', 'jjn', 'atkinson'.`)
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flag.Var(ditherOpts, "o",
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`Supply options for the selected ditherer.
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Currently only relevant to the bayer ditherer, which defaults to 'level 0, non-inverted'.
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To change: '1' applies a level-one bayer diffuser; '1n' would invert it, '0' would be the default.`)
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outputFlag := flag.String("out", "output.png", "Output filename. Outputs in PNG format.")
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flag.Parse()
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// extract all those pointers
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filename := *filenameFlag
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ditherer := *dithererFlag
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palette := *paletteFlag
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outfile := *outputFlag
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verbose := *verboseFlag
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if filename == "" || outfile == "" {
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fmt.Printf("Usage of %s:\n", os.Args[0])
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flag.PrintDefaults()
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os.Exit(0)
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}
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filename := os.Args[1]
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ditherer := os.Args[2]
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outfile := os.Args[3]
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i, codex, err := loadImage(filename)
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if err != nil {
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fmt.Printf("error loading %s; %v\n", filename, err)
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os.Exit(255)
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}
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fmt.Printf("loaded %s using %s\n", filename, codex)
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if verbose {
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fmt.Printf("loaded %s using %s\n", filename, codex)
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}
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t := time.Now()
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@ -59,33 +108,50 @@ func main() {
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case "noop":
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new = apply(i, noOp)
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case "naive":
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new = apply(i, naiveBW)
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case "palette":
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new = apply(i, naivePalette(sixteencolors))
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case "randomnoise":
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if palette == "bw" {
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new = apply(i, naiveBW)
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} else if palette == "sixteen" {
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new = apply(i, naivePalette(sixteencolors))
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}
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case "noise":
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rand.Seed(time.Now().UnixNano())
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new = apply(i, randomNoise)
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case "noisepalette":
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rand.Seed(time.Now().UnixNano())
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new = apply(i, randomNoisePalette(sixteencolors))
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case "bayer0":
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new = apply(i, bayerDithering(0, false))
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case "bayer0p":
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new = apply(i, colorBayer(0, sixteencolors))
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case "bayer0n":
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new = apply(i, bayerDithering(0, true))
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case "bayer1":
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new = apply(i, bayerDithering(1, false))
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case "bayer1n":
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new = apply(i, bayerDithering(1, true))
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case "bayer1p":
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new = apply(i, colorBayer(1, sixteencolors))
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case "simpleerror":
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new = apply(i, simpleErrorDiffusion())
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if palette == "bw" {
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new = apply(i, randomNoise)
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} else if palette == "sixteen" {
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new = apply(i, randomNoisePalette(sixteencolors))
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} else {
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fmt.Printf("unknown palette option for %s ditherer: %s\n", ditherer, palette)
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os.Exit(2)
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}
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case "bayer":
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if palette == "bw" {
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new = apply(i, bayerDithering(ditherOpts.level, ditherOpts.invert))
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} else if palette == "sixteen" {
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new = apply(i, colorBayer(ditherOpts.level, sixteencolors))
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} else {
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fmt.Printf("unknown palette option for %s ditherer: %s\n", ditherer, palette)
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os.Exit(2)
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}
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case "error":
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if palette == "bw" {
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new = apply(i, simpleErrorDiffusion())
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} else if palette == "sixteen" {
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new = apply(i, simpleColorErrorDiffusion())
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} else {
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fmt.Printf("unknown palette option for %s ditherer: %s\n", ditherer, palette)
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os.Exit(2)
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}
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case "floydsteinberg":
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new = apply(i, floydSteinberg())
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case "jjn":
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new = apply(i, jarvisJudiceNinke())
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if palette == "bw" {
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new = apply(i, jarvisJudiceNinke())
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} else if palette == "sixteen" {
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new = apply(i, colorJarvisJudiceNinke())
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} else {
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fmt.Printf("unknown palette option for %s ditherer: %s\n", ditherer, palette)
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os.Exit(2)
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}
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case "atkinson":
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new = apply(i, atkinson())
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default:
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@ -93,14 +159,19 @@ func main() {
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os.Exit(2)
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}
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fmt.Printf("dithering took %s\n", time.Since(t))
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if verbose {
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fmt.Printf("dithering took %s\n", time.Since(t))
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}
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err = saveImage(outfile, new)
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if err != nil {
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fmt.Printf("error saving %s; %v\n", outfile, err)
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os.Exit(255)
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}
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fmt.Printf("saved output to %s\n", outfile)
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if verbose {
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fmt.Printf("saved output to %s\n", outfile)
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}
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}
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func loadImage(filename string) (image.Image, string, error) {
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