JPG to PNG converter in pure Go

jpg2png.go

package main

import (
	"flag"
	"io"
	"log"
	"os"

	jpg "image/jpeg"
	"image/png"
)

var in = flag.String("in", "", "Input JPEG image.")
var out = flag.String("out", "", "Input JPEG image.")

func JPEG2PNG(fin io.Reader, fout io.Writer) error {
	img, err := jpg.Decode(fin)

	if err != nil {
		return err
	}

	return png.Encode(fout, img)
}

func main() {
	flag.Parse()

	fin, err := os.Open(*in)

	if err != nil {
		log.Fatalf("failed to open input file: %s", err)
	}

	defer fin.Close()

	fout, err := os.Create(*out)

	if err != nil {
		log.Fatalf("failed to open output file: %s", err)
	}

	defer fout.Close()

	if err := JPEG2PNG(fin, fout); err != nil {
		log.Fatal(err)
	}
}