Go で画像を JPEG に変換

ConvertToJpeg

package main

import (
	"flag"
	"image"
	_ "image/gif"
	"image/jpeg"
	_ "image/png"
	"log"
	"os"
)

func main() {
	var (
		src     = flag.String("s", "", "JPEG に変換したい画像パス")
		dest    = flag.String("d", "", "JEPG に変換した画像パス")
		quality = flag.Int("q", 100, "JPEG 変換時の Quality")
	)

	flag.Parse()

	convertToJpeg(*src, *dest, *quality)
}

func convertToJpeg(src string, dest string, quality int) {
	file, err := os.Open(src)
	logError(err)
	defer file.Close()

	img, _, err := image.Decode(file)
	logError(err)

	out, err := os.Create(dest)
	logError(err)
	defer out.Close()

	opts := &jpeg.Options{Quality: quality}

	jpeg.Encode(out, img, opts)
}

func logError(err error) {
	if err != nil {
		log.Fatal(err)
		os.Exit(1)
	}
}