Convert image in folder to resize them

convert-img-in-folder.go

// Note: You have to install imagemagick before
package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
)

type FileInfo struct {
	name      string
	extension string
	size      int64
}

func (fi FileInfo) String() string {
	formatedName := rightPad(fi.name, 50)
	formatedExtension := rightPad(fi.extension, 10)
	formatedSize := rightPad(strconv.FormatInt(fi.size, 10), 20)
	return fmt.Sprintf("%s %s %s", formatedName, formatedExtension, formatedSize)
}

func rightPad(s string, length int) string {
	sLen := len(s)
	if sLen >= length {
		return s
	}
	for i := 0; i < length-sLen; i++ {
		s += " "
	}
	return s
}

func main() {
	rootDir := "your_dir"
	listImageFileInDir(rootDir)
}

func listImageFileInDir(rootDir string) {
	var files []FileInfo

	//  Scan file
	err := filepath.Walk(rootDir, func(path string, info os.FileInfo, err error) error {
		fileNameIndex := strings.LastIndex(path, "/") + 1
		fileName := path[fileNameIndex:]
		fileTypeIndex := strings.LastIndex(fileName, ".")
		if fileTypeIndex > 0 {
			fileType := fileName[fileTypeIndex:]
			matchImageType, _ := regexp.MatchString("(png|jpg)", fileType)
			if matchImageType {
				fileInfo := FileInfo{
					name:      fileName,
					extension: fileType,
					size:      info.Size(),
				}
				files = append(files, fileInfo)
			}
		}
		return nil
	})

	if err != nil {
		panic(err)
	}

	// sort by size
	sort.Slice(files[:], func(i, j int) bool {
		return files[i].size > files[j].size
	})

	for _, file := range files {
		fmt.Println(file)
	}

	for _, file := range files {
		convertImg(file.name, file.extension)
	}
}

func getFileSize(file string) int64 {
	fi, err := os.Stat(file)
	if err != nil {
		log.Fatal(err)
	}
	return fi.Size()
}

func convertImg(fileName string, fileType string) {
	convertedFileName := "conveted_" + fileName

	// open file to append
	file, err := os.OpenFile("convert_result.txt", os.O_APPEND|os.O_WRONLY, os.ModeAppend)
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()
	w := bufio.NewWriter(file)

	// convert file
	fileSizeBeforeConvert := getFileSize(fileName)
	fmt.Fprintf(w, "File size of %s before convert: %d\n", fileName, fileSizeBeforeConvert)
	if fileType == ".png" {
		_, err := exec.Command("convert", fileName, "-strip", convertedFileName).Output()
		if err != nil {
			log.Fatal(err)
		}
		fileSizeAfterConvert := getFileSize(convertedFileName)
		fmt.Fprintf(w, "File size of %s after convert: %d\n", fileName, fileSizeAfterConvert)
		fmt.Fprintln(w, "======================================================================")
	} else if fileType == ".jpg" {
		_, err := exec.Command("convert", fileName, "-sampling-factor", "4:2:0", "-strip", "-quality", "100", "-interlace", "JPEG", "-colorspace", "sRGB", convertedFileName).Output()
		if err != nil {
			log.Fatal(err)
		}
		fileSizeAfterConvert := getFileSize(convertedFileName)
		fmt.Fprintf(w, "File size of %s after convert: %d\n", fileName, fileSizeAfterConvert)
		fmt.Fprintln(w, "======================================================================")
	}
	w.Flush()
}