tranform.go

package main

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

func main() {
	imgfile, err := os.Open("/home/prl900/Downloads/red.png")
	if err != nil {
		fmt.Println("file not found!")
		os.Exit(1)
	}

	img, _ := png.Decode(imgfile)
	imgfile.Close()

	red := img.(*image.NRGBA64)

	gray := image.NewGray16(red.Bounds())

	for i := 0; i < red.Bounds().Max.X; i++ {
		for j := 0; j < red.Bounds().Max.Y; j++ {
			val := red.NRGBA64At(i, j)
			if val.R != 32767 {
				gray.SetGray16(i, j, color.Gray16{val.R})
			}
		}
	}

	out, err := os.Create("/home/prl900/Downloads/gray.png")
	err = png.Encode(out, gray)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}