Implements imgconv

Author: tanaka0325

kadai1/tanaka0325/README.md

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+# Image Converter
+
+## Spec
+
+```
+## 次の仕様を満たすコマンドを作って下さい
+
+- ディレクトリを指定する
+- 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する
+- 変換前と変換後の画像形式を指定できる（オプション）
+
+## 以下を満たすように開発してください
+
+- mainパッケージと分離する
+- 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使う
+- 準標準パッケージ：golang.org/x以下のパッケージ
+- ユーザ定義型を作ってみる
+- GoDocを生成してみる
+- Go Modulesを使ってみる
+```
+
+## Usage
+
+```zsh
+# build
+$ go build -o ./imgconv
+
+# display help
+$ ./imgconv -h
+Usage of ./imgconv:
+  -f string
+        file extention before convert (default "jpg")
+  -n    dry run
+  -t string
+        file extention after convert (default "png")
+
+# single directory
+$ ./imgconv images
+
+# multi directories
+$ ./imgconv images images2
+
+# customize ext
+$ ./imgconv -f png -t gif images
+
+# dry run
+$ ./imgconv -n images
+images/sample1.jpg => images/sample1.png
+images2/img/sample3.jpg => images2/img/sample3.png
+images2/sample2.jpg => images2/sample2.png
+```
+
+## 感想
+
+- long option(?) はどうやってやれば良いのだろうか
+- そもそも作りとしてこれで良いのだろうか・・・めっちゃ悩みました
+

kadai1/tanaka0325/converter/conv_image.go

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+package converter
+
+import (
+	"fmt"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+	"io"
+	"os"
+
+	"golang.org/x/image/bmp"
+	"golang.org/x/image/tiff"
+)
+
+type convImage struct {
+	filename string
+	fromExt  string
+	toExt    string
+	image    image.Image
+}
+
+func (i *convImage) decode() error {
+	r, err := os.Open(i.filename + "." + i.fromExt)
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+
+	img, err := decodeHelper(r, i.fromExt)
+	if err != nil {
+		return fmt.Errorf("decode error: %w", err)
+	}
+
+	i.image = img
+	return nil
+}
+
+func decodeHelper(r io.Reader, ext string) (image.Image, error) {
+	switch ext {
+	case "png":
+		return png.Decode(r)
+	case "jpg", "jpeg":
+		return jpeg.Decode(r)
+	case "gif":
+		return gif.Decode(r)
+	case "bmp":
+		return bmp.Decode(r)
+	case "tiff", "tif":
+		return tiff.Decode(r)
+	}
+	return nil, fmt.Errorf("%s is not allowed", ext)
+}
+
+func (i *convImage) encode() error {
+	w, err := os.Create(i.filename + "." + i.toExt)
+	if err != nil {
+		return err
+	}
+	defer func() error {
+		if err := w.Close(); err != nil {
+			return err
+		}
+		return nil
+	}()
+
+	switch i.toExt {
+	case "png":
+		return png.Encode(w, i.image)
+	case "jpg", "jpeg":
+		return jpeg.Encode(w, i.image, nil)
+	case "gif":
+		return gif.Encode(w, i.image, nil)
+	case "bmp":
+		return gif.Encode(w, i.image, nil)
+	case "tiff", "tif":
+		return gif.Encode(w, i.image, nil)
+	}
+
+	return fmt.Errorf("cannot encode image")
+}

kadai1/tanaka0325/converter/convert.go

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+package converter
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// flags
+var (
+	allowedExts = exts{"png", "jpg", "jpeg", "gif", "bmp", "tiff", "tif"}
+	f           = flag.String("f", "jpg", "file extention before convert")
+	t           = flag.String("t", "png", "file extention after convert")
+	dryRun      = flag.Bool("n", false, "dry run")
+)
+
+// Convert is to convert image file format
+func Convert() {
+	// check options ext
+	flag.Parse()
+	to := strings.ToLower(*t)
+	from := strings.ToLower(*f)
+	targetExts := []string{to, from}
+	for _, e := range targetExts {
+		if err := allowedExts.include(e); err != nil {
+			log.Fatal(fmt.Errorf("%w. ext is only allowd in %s", err, allowedExts))
+		}
+	}
+
+	// get target image paths from args
+	dns := flag.Args()
+	udns := uniq(dns)
+	paths, err := getPaths(udns, from)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// convert
+	imgs, err := createConvImages(paths, from, to)
+	if err != nil {
+		log.Fatal(err)
+	}
+	for _, img := range imgs {
+		if err := img.decode(); err != nil {
+			log.Fatal(err)
+		}
+
+		if *dryRun {
+			fmt.Println(img.filename+"."+img.fromExt, "=>", img.filename+"."+img.toExt)
+		} else {
+			if err := img.encode(); err != nil {
+				log.Fatal(err)
+			}
+		}
+	}
+}
+
+func uniq(s []string) []string {
+	m := map[string]bool{}
+	u := []string{}
+
+	for _, v := range s {
+		if !m[v] {
+			m[v] = true
+			u = append(u, v)
+		}
+	}
+
+	return u
+}
+
+func getPaths(dns []string, from string) ([]string, error) {
+	paths := []string{}
+
+	for _, dn := range dns {
+		if err := filepath.Walk(dn, func(path string, info os.FileInfo, err error) error {
+			if filepath.Ext(path) == "."+from {
+				paths = append(paths, path)
+			}
+			return nil
+		}); err != nil {
+			return nil, err
+		}
+	}
+
+	return paths, nil
+}
+
+func createConvImages(paths []string, from, to string) ([]convImage, error) {
+	images := []convImage{}
+	for _, p := range paths {
+		i := convImage{
+			filename: strings.Replace(p, "."+from, "", 1),
+			fromExt:  strings.ToLower(from),
+			toExt:    strings.ToLower(to),
+		}
+		images = append(images, i)
+	}
+
+	return images, nil
+}

kadai1/tanaka0325/converter/exts.go

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+package converter
+
+import "errors"
+
+type exts []string
+
+func (es exts) include(w string) error {
+	for _, e := range es {
+		if e == w {
+			return nil
+		}
+	}
+	return errors.New(w + " is not allowed")
+}

kadai1/tanaka0325/go.mod

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+module github.com/gopherdojo/dojo8/kadai1/tanaka0325
+
+go 1.14
+
+require golang.org/x/image v0.0.0-20200618115811-c13761719519

kadai1/tanaka0325/go.sum

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+github.com/gopherdojo/dojo8 v0.0.0-20200703052727-6a79d18126bf h1:lpYevjFQMxI5VNBc3WXV6Z5pDDrdppdDKwmeBoyt5BE=
+golang.org/x/image v0.0.0-20200618115811-c13761719519 h1:1e2ufUJNM3lCHEY5jIgac/7UTjd6cgJNdatjPdFWf34=
+golang.org/x/image v0.0.0-20200618115811-c13761719519/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

kadai1/tanaka0325/images/sample1.jpg

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+package main
+
+import "github.com/gopherdojo/dojo8/kadai1/tanaka0325/converter"
+
+func main() {
+	converter.Convert()
+}