lab4-diff.go

package main

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

func mustReadImage(filename string) image.Image {
	file, err := os.Open(filename)
	if err != nil {
		fmt.Fprintf(os.Stderr, "error opening %s: %s\n", filename, err)
		os.Exit(66)
	}
	img, err := png.Decode(file)
	if err != nil {
		fmt.Fprintf(os.Stderr, "error decoding %s: %s\n", filename, err)
		os.Exit(66)
	}
	return img
}

func exitResult(passed bool) {
	if !passed {
		fmt.Println("Rejected")
		os.Exit(66)
	} else {
		fmt.Println("Accepted")
		os.Exit(0)
	}
}

func main() {
	if len(os.Args) != 3 {
		fmt.Fprintf(os.Stderr, "usage: %s ref.png out.png\n", os.Args[0])
		os.Exit(87)
	}
	img0 := mustReadImage(os.Args[1])
	img1 := mustReadImage(os.Args[2])
	rect0 := img0.Bounds()
	rect1 := img1.Bounds()
	if !rect0.Eq(rect1) {
		fmt.Println("different shape", rect0, rect1)
		exitResult(false)
	}
	total := rect0.Dx() * rect0.Dy()
	same := 0
	for x := rect0.Min.X; x < rect0.Max.X; x++ {
		for y := rect0.Min.Y; y < rect0.Max.Y; y++ {
			color0 := img0.At(x, y)
			color1 := img1.At(x, y)
			r0, g0, b0, a0 := color0.RGBA()
			r1, g1, b1, a1 := color1.RGBA()
			if r0 == r1 && g0 == g1 && b0 == b1 && a0 == a1 {
				same++
			}
		}
	}
	fmt.Printf("%v/%v\n", same, total)
	exitResult(same == total)
}