74 lines
1.3 KiB
Go
74 lines
1.3 KiB
Go
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package main
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import (
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"errors"
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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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"image/png"
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"log"
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"os"
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)
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func run() error {
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flag.Parse()
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args := flag.Args()
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if len(args) < 1 {
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return errors.New("no command specified")
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}
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switch args[0] {
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case "setalpha":
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flags := flag.NewFlagSet("setalpha", flag.ContinueOnError)
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var alpha int
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flags.IntVar(&alpha, "alpha", 127, "sets the target alpha")
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flags.Parse(args[1:])
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for _, path := range flags.Args() {
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err := setAlpha(path, alpha)
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if err != nil {
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return fmt.Errorf("couldn't set alpha for '%s'; error: %v", path, err)
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}
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}
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}
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return nil
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}
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func setAlpha(path string, alpha int) error {
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src, err := os.Open(path)
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if err != nil {
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return err
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}
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defer src.Close()
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im, _, err := image.Decode(src)
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if err != nil {
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return err
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}
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bounds := im.Bounds()
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dst := image.NewNRGBA(bounds)
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for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
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for x := bounds.Min.X; x < bounds.Max.X; x++ {
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c := color.NRGBAModel.Convert(im.At(x, y)).(color.NRGBA)
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if c.A > 0 {
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c.A = uint8(alpha)
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}
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dst.Set(x, y, c)
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}
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}
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return encodePNG(path, dst)
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}
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func encodePNG(path string, im image.Image) error {
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dst, err := os.Create(path)
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if err != nil {
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return err
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}
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defer dst.Close()
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return png.Encode(dst, im)
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}
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func main() {
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if err := run(); err != nil {
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log.Fatal(err)
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}
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}
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