PNG をR,G,Bに分解

png_separate_rgb.go

package main

// http://blog.golang.org/go-image-package
// http://d.hatena.ne.jp/taknb2nch/20131231/1388500659

import (
        "flag"
        "fmt"
        "image"
	"image/color"
        "image/png"
        "os"
)

func main() {
        flag.Parse()
        file_in := flag.Arg(0)
        file_out := flag.Arg(1)
        fd_in, err := os.Open(file_in)
        if err != nil {
                fmt.Fprintln(os.Stderr, "not found:"+file_in)
                os.Exit(1)
        }
        fd_out, err := os.Create(file_out)
        if err != nil {
                fmt.Fprintln(os.Stderr, "not found:"+file_out)
                os.Exit(1)
        }
	image_in, _ := png.Decode(fd_in)
        rect := image_in.Bounds()
	size := rect.Size()

        image_out := image.NewNRGBA(image.Rect(0, 0, 3*size.X, size.Y))

        for y := 0; y < size.Y; y++ {
                for x := 0; x < size.X; x++ {
                        r, g, b, a := image_in.At(x, y).RGBA()
                        image_out.Set(x, y, color.RGBA{uint8(r), 0, 0, uint8(a)\
})
  			image_out.Set(size.X+x, y, color.RGBA{0, uint8(g), 0, u\
int8(a)})
                        image_out.Set(2*size.X+x, y, color.RGBA{0, 0, uint8(b),\
 uint8(a)})
                }
	}
	png.Encode(fd_out, image_out)
}