Kadai1 karasuex54

kadai1/karasuex54/README.md

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+# 画像変換コマンドを作ろう
+
+## 次の仕様を満たすコマンドを作成
+- ディレクトリを指定
+- 指定したディレクトリ以下のJPGファイルをPNGに変換（デフォルト）
+- ディレクトリ以下は再帰的に処理
+- 変換前と変換後の画像形式を指定可能（オプション）
+
+## 以下を満たすように開発
+- mainパッケージと分離
+- 自作パッケージと標準パッケージと準標準パッケージのみを使用
+  - 準標準パッケージ：golang.org/x以下のパッケージ
+- ユーザ定義型を作成
+- GoDocを生成
+- Go Modulesを使用
+
+## 使い方
+1.バイナリファイル作成
+```sh
+go build -o main
+```
+
+2.コマンド実行
+```sh
+./main -from=[jpg|jpeg|png|gif] -to=[jpg|jpeg|png|gif] <変換する画像の入ったフォルダのパス>
+```

kadai1/karasuex54/converter/converter.go

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+// Package converter is image file convert package.
+package converter
+
+import (
+	"fmt"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// Converter is a struct that has target directory, target file extention and convert file extention.
+type Converter struct {
+	targetDir string
+	fromExt   string
+	toExt     string
+}
+
+type Option func(*Converter) error
+
+func FromExt(ext string) Option {
+	return func(c *Converter) error {
+		c.fromExt = ext
+		return nil
+	}
+}
+
+func ToExt(ext string) Option {
+	return func(c *Converter) error {
+		c.toExt = ext
+		return nil
+	}
+}
+
+// Decode reads an image from r and returns it as an image.Image.
+func (c Converter) Decode(r io.Reader) (image.Image, error) {
+	switch c.fromExt {
+	case "png":
+		return png.Decode(r)
+	case "jpg", "jpeg":
+		return jpeg.Decode(r)
+	case "gif":
+		return gif.Decode(r)
+	default:
+		return nil, fmt.Errorf("fail setting Converter.fromExt")
+	}
+}
+
+// Encode writes the Image m to w in c.toExt format.
+func (c Converter) Encode(w io.Writer, m image.Image) error {
+	switch c.toExt {
+	case "png":
+		return png.Encode(w, m)
+	case "jpg", "jpeg":
+		return jpeg.Encode(w, m, &jpeg.Options{Quality: 100})
+	case "gif":
+		return gif.Encode(w, m, &gif.Options{NumColors: 256})
+	default:
+		return fmt.Errorf("fail setting Converter.toExt")
+	}
+}
+
+// Convert reads an image file from path, creates a file, and writes to it in c.toExt format.
+func (c Converter) Convert(path string) error {
+	sf, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer sf.Close()
+	img, err := c.Decode(sf)
+	if err != nil {
+		return err
+	}
+	fileName := filepath.Base(path)
+	convertedPath := fileName[:len(fileName)-len(filepath.Ext(path))] + "." + c.toExt
+	df, err := os.Create(convertedPath)
+	if err != nil {
+		return err
+	}
+	defer df.Close()
+	err = c.Encode(df, img)
+	if err != nil {
+		if removeErr := os.Remove(convertedPath); removeErr != nil {
+			return removeErr
+		}
+		return err
+	}
+	return nil
+}
+
+// Run finds files of c.fromExt form in the directories and files under c.targetDir. It passes the path of the file as an argument to c.Convert().
+func (c Converter) Run() {
+	ext := "." + c.fromExt
+	err := filepath.Walk(c.targetDir,
+		func(path string, info os.FileInfo, err error) error {
+			if filepath.Ext(path) == ext {
+				c.Convert(path)
+			}
+			return nil
+		})
+	if err != nil {
+		fmt.Println("error :", err)
+		return
+	}
+}
+
+// NewConverter returns c.Converter.
+func NewConverter(dirPath string, options ...Option) *Converter {
+	c := Converter{
+		targetDir: dirPath,
+		fromExt:   "jpg",
+		toExt:     "png",
+	}
+	for _, option := range options {
+		option(&c)
+	}
+	return &c
+}

kadai1/karasuex54/go.mod

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+module github.com/karasuex54/gopherdojo-studyroom/kadai1/karasuex54
+
+go 1.17

kadai1/karasuex54/main.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"github.com/karasuex54/gopherdojo-studyroom/kadai1/karasuex54/converter"
+)
+
+var (
+	targetDir string
+	fromExt   string
+	toExt     string
+)
+
+func main() {
+	flag.StringVar(&fromExt, "from", "jpg", "target image file extention")
+	flag.StringVar(&toExt, "to", "png", "convert image file extention")
+	flag.Parse()
+
+	args := flag.Args()
+	switch len(args) {
+	case 0:
+		fmt.Println("few arguments")
+		return
+	case 1:
+		targetDir = args[0]
+	default:
+		fmt.Println("too arguments")
+		return
+	}
+
+	c := converter.NewConverter(targetDir, converter.FromExt(fromExt), converter.ToExt(toExt))
+	c.Run()
+}