grayscale_four.go

func parseExt(path string) string {
	split := strings.Split(path, ".")
	return "." + split[len(split)-1]
}

func today() string {
	now := time.Now()
	return now.Format("20060102")
}

func main() {
  
    	...
  
 	newExt := parseExt(f.Name)
	newFile := *dest + "/" + f.Name[0:len(f.Name)-len(newExt)] + "_GRAYSCALED_" + today() + newExt
	out, err := os.Create(newFile)
	if err != nil {
		fmt.Printf("error creating destination image path '%s': %s\n", newFile, err.Error())
		continue
	}
	defer out.Close()

	err = jpeg.Encode(out, gray, nil)
	if err != nil {
		fmt.Printf("error saving image at destination '%s': %s\n", newFile, err.Error())
		continue
	} 
}