change a pixel #ff00ff color to transparency with golang

convert_pixel_color.go

package main

import (
	"fmt"
	"image/color"
	"image/png"
	"os"
	"path/filepath"
	"strings"
)

type Changeable interface {
	Set(x, y int, c color.Color)
}

var (
	PinkTransparecyColor = color.RGBA{R: 255, B: 255, A: 255} // #ff00ff
)

func main() {
  
	imgfile, err := os.Open("spritesheet.png")
	if err != nil {
		panic(err.Error())
	}
	defer imgfile.Close()

	img, err := png.Decode(imgfile)
	if err != nil {
		panic(err.Error())
	}
	if cimg, ok := img.(Changeable); ok {
		for y := 0; y < img.Bounds().Max.Y; y++ {
			for x := 0; x < img.Bounds().Max.X; x++ {
				if img.At(x, y) == PinkTransparecyColor {
					cimg.Set(x, y, color.RGBA{0, 0, 0, 0})
				}
			}
		}
		ext := filepath.Ext("spritesheet.png")
		name := strings.TrimSuffix(filepath.Base("spritesheet.png"), ext)
		fg := &os.File{}
		fg, err = os.Create(fmt.Sprintf("%s_go_removed_transparency%s", name, ext))
		if err != nil {
			panic(err)
		}
		defer fg.Close()
		err = png.Encode(fg, img)
		if err != nil {
			panic(err)
		}
	}else{
    panic("encoded image not support set(x, y, color.Color) function")
	}

}