Error level analys for JPEG in Golang

ela.go

package main

import (
	"bytes"
	"flag"
	"image"
	"image/jpeg"
	_ "image/png"
	"os"
)

const amplifier = 10

func diff(x, y uint8) uint8 {
	if x > y {
		return x - y
	}
	return y - x
}

func panicIf(err error) {
	if err != nil {
		panic(err)
	}
}

func DrawELA(input, output string) {
	inReader, err := os.Open(input)
	panicIf(err)

	inStat, err := inReader.Stat()
	panicIf(err)

	outWriter, err := os.Create(output)
	panicIf(err)

	src, _, err := image.Decode(inReader)
	panicIf(err)

	bounds := src.Bounds()

	srcRGBA, ok := src.(*image.RGBA)
	if !ok {
		panic("can not convert src to RGBA")
	}

	buf := bytes.NewBuffer(make([]byte, 0, inStat.Size()*2))
	err = jpeg.Encode(buf, src, &jpeg.Options{95})
	panicIf(err)

	sample, err := jpeg.Decode(buf)
	panicIf(err)

	sampleRGBA, ok := sample.(*image.RGBA)
	if !ok {
		panic("can not convert sample to RGBA")
	}

	for x := bounds.Min.X; x < bounds.Max.X; x++ {
		for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
			i := srcRGBA.PixOffset(x, y)
			srcRGBA.Pix[i] = diff(srcRGBA.Pix[i], sampleRGBA.Pix[i]) * amplifier
			srcRGBA.Pix[i+1] = diff(srcRGBA.Pix[i+1], sampleRGBA.Pix[i+1]) * amplifier
			srcRGBA.Pix[i+2] = diff(srcRGBA.Pix[i+2], sampleRGBA.Pix[i+2]) * amplifier
		}
	}

	err = jpeg.Encode(outWriter, srcRGBA, &jpeg.Options{95})
	panicIf(err)
}

func main() {
	var input *string = flag.String("input", "", "input stream")
	var output *string = flag.String("output", "", "output stream")
	flag.Parse()

	DrawELA(*input, *output)
}