thumbnail generate, use vipsthumbnail cmdtool which comes from libvips. It takes 0.3s to generate a thumbnail from a 5Mbyte photo on one cpu core.

resize.go

func ResizeImg(spath string, tpath []string, size []image.Point) (int, error) {
	if len(tpath) != len(size) {
		log.Println("GetImgThumb: ", tpath, size)
		return 0, errors.New("GetImgThumb length unsafe")
	}

	cnt := 0
	for i, tgt := range tpath {
		log.Println("+++", spath, tgt)
		_, err := os.Stat(tgt)
		if err != nil {
			if !os.IsNotExist(err) {
				log.Println(err)
				continue
			}
			// 创建文件夹
			os.MkdirAll(filepath.Dir(tgt), 0755)
			log.Println("=== ", tgt)
			cmd := exec.Command("vipsthumbnail", spath, "-o", tgt, "-s", strconv.Itoa(size[i].X))
			err := cmd.Run()
			if err != nil {
				log.Println("run err:", spath, tgt, err)
			}
			cnt++
		}
	}

	return cnt, nil
}