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)
    }
}