Created
December 23, 2021 10:17
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| package main | |
| import ( | |
| "fmt" | |
| "image" | |
| "log" | |
| "os" | |
| "path/filepath" | |
| "strings" | |
| "image/color" | |
| "image/gif" | |
| "image/jpeg" | |
| "image/png" | |
| ) | |
| func main() { | |
| if len(os.Args) < 3 { | |
| fmt.Fprintln(os.Stderr, "usage: bwdith <infile> <outfile>") | |
| os.Exit(1) | |
| } | |
| in, err := os.Open(os.Args[1]) | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| defer in.Close() | |
| src, _, err := image.Decode(in) | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| bounds := src.Bounds() | |
| dst := image.NewGray(bounds) | |
| for y := bounds.Min.Y; y < bounds.Max.Y; y++ { | |
| var qerr uint8 | |
| for x := bounds.Min.X; x < bounds.Max.X; x++ { | |
| gs := color.GrayModel.Convert(src.At(x, y)).(color.Gray) | |
| // distance from white, no need for dfb because that's just gs.Y | |
| oldY := dst.At(x, y).(color.Gray).Y | |
| var dfw uint8 | |
| if oldY > 0 { | |
| dfw = 255 - oldY | |
| if dfw < oldY { | |
| qerr = dfw | |
| dst.Set(x, y, color.White) | |
| } else { | |
| qerr = oldY | |
| dst.Set(x, y, color.Black) | |
| } | |
| } else { | |
| dfw = 255 - gs.Y | |
| if dfw < gs.Y { | |
| qerr = dfw | |
| dst.Set(x, y, color.White) | |
| } else { | |
| qerr = gs.Y | |
| dst.Set(x, y, color.Black) | |
| } | |
| } | |
| dst.Set(x+1, y, &color.Gray{qerr * 7 / 16}) | |
| dst.Set(x-1, y+1, &color.Gray{qerr * 3 / 16}) | |
| dst.Set(x, y+1, &color.Gray{qerr * 5 / 16}) | |
| dst.Set(x+1, y+1, &color.Gray{qerr * 1 / 16}) | |
| } | |
| } | |
| out, _ := os.OpenFile(fmt.Sprintf("%s", os.Args[2]), os.O_WRONLY|os.O_CREATE, 0600) | |
| defer out.Close() | |
| switch strings.TrimPrefix(filepath.Ext(os.Args[2]), ".") { | |
| case "jpg", "jpeg": | |
| jpeg.Encode(out, dst, nil) | |
| case "png": | |
| png.Encode(out, dst) | |
| case "gif": | |
| gif.Encode(out, dst, nil) | |
| default: | |
| fmt.Fprintln(os.Stderr, "error: output format not supported") | |
| } | |
| } | |
| // getOutName returns a usable name for the outFile. | |
| func getOutName() string { | |
| return "out.png" | |
| } |
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