Kadai2 lfcd85

kadai2/lfcd85/.gitignore

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+bin/convert

kadai2/lfcd85/Makefile

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+bin/convert: cmd/convert/*.go imgconv/*.go
+	GO111MODULE=on go build -o bin/convert cmd/convert/main.go
+
+fmt:
+	go fmt ./...
+	go vet ./...
+
+check:
+	GO111MODULE=on go test ./imgconv/... -v
+
+coverage:
+	GO111MODULE=on go test ./imgconv/... -cover

kadai2/lfcd85/README.md

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+# imgconv
+
+An implementation for the image conversion command, kadai-1 of Gopherdojo #5.
+
+Gopher道場 #5 課題1 `画像変換コマンド` の実装です。
+
+## Installation
+
+```bash
+$ make bin/convert
+```
+
+## Usage
+
+Specify the target directory as an argument. The given directory is recursively processed. Converted files are outputted under `./output/` directory.
+
+コマンド引数に対象ディレクトリを指定してください。ディレクトリ以下は再帰的に処理されます。変換後のファイルは `./output/` ディレクトリ以下に出力されます。
+
+```bash
+$ bin/convert test/
+```
+
+Input and output image formats can be set by `-f` (from) and `-t` (to) options. Default formats are from JPEG to PNG. JPEG, PNG, GIF are available.
+
+画像形式は `-f` オプション（変換前）・ `-t` オプション（変換後）で指定できます。デフォルトは JPEG → PNG です。JPEG, PNG, GIF 形式が利用可能です。
+
+```bash
+$ bin/convert -f png -t jpeg test/
+```

kadai2/lfcd85/cmd/convert/main.go

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+// Command bin/convert ...
+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"github.com/gopherdojo/dojo5/kadai2/lfcd85/imgconv"
+)
+
+func main() {
+	from := flag.String("f", "jpeg", "Image format before conversion (default: jpeg)")
+	to := flag.String("t", "png", "Image format after conversion (default: png)")
+	flag.Parse()
+	dirName := flag.Arg(0)
+
+	err := imgconv.Convert(dirName, *from, *to)
+	if err != nil {
+		fmt.Println("error:", err)
+		return
+	}
+}

kadai2/lfcd85/go.mod

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+module github.com/gopherdojo/dojo5/kadai2/lfcd85
+
+go 1.12

kadai2/lfcd85/imgconv/imgconv.go

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+// Package imgconv provides a recursive conversion of images in the directory.
+package imgconv
+
+import (
+	"errors"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// MapImgFmtExts is a map of the image formats and its extensions.
+type MapImgFmtExts map[ImgFmt]Exts
+
+// Exts is a slice of image extensions.
+type Exts []Ext
+
+// Ext is a image extension.
+type Ext string
+
+// ImgFmt is a image format.
+type ImgFmt string
+
+// Converter is a struct which contains info about image formats and extensions.
+type Converter struct {
+	fmtFrom    ImgFmt
+	fmtTo      ImgFmt
+	imgFmtExts MapImgFmtExts
+}
+
+// Convert recursively seeks a given directory and converts images from and to given formats.
+func Convert(dir string, from string, to string) error {
+	if dir == "" {
+		return errors.New("directory name is not provided")
+	}
+
+	cv := &Converter{}
+	cv.imgFmtExts.Init()
+	cv.fmtFrom.Detect(cv, from)
+	cv.fmtTo.Detect(cv, to)
+	if cv.fmtFrom == "" || cv.fmtTo == "" {
+		return errors.New("given image format is not supported")
+	}
+	if cv.fmtFrom == cv.fmtTo {
+		return errors.New("image formats before and after conversion are the same")
+	}
+
+	err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		err = cv.convSingleFile(path, info)
+		return err
+	})
+	return err
+}
+
+func (cv *Converter) convSingleFile(path string, info os.FileInfo) error {
+	if info.IsDir() {
+		outputPath := addOutputDir(path)
+		return os.MkdirAll(outputPath, 0777)
+	}
+	if !cv.fmtFrom.Match(cv, info.Name()) {
+		return nil
+	}
+
+	f, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	img, err := cv.decodeImg(f)
+	if err != nil {
+		return nil
+	}
+
+	return cv.writeOutputFile(img, path)
+}
+
+func (cv *Converter) writeOutputFile(img image.Image, path string) error {
+	outputPath := cv.generateOutputPath(path)
+
+	f, err := os.Create(outputPath)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	err = cv.encodeImg(f, img)
+	return err
+}
+
+func (cv *Converter) decodeImg(r io.Reader) (image.Image, error) {
+	img, fmtStr, err := image.Decode(r)
+	if ImgFmt(fmtStr) != cv.fmtFrom {
+		err = errors.New("image format does not match")
+	}
+	return img, err
+}
+
+func (cv *Converter) encodeImg(w io.Writer, img image.Image) error {
+	switch cv.fmtTo {
+	case "jpeg":
+		if err := jpeg.Encode(w, img, nil); err != nil {
+			return err
+		}
+	case "png":
+		if err := png.Encode(w, img); err != nil {
+			return err
+		}
+	case "gif":
+		if err := gif.Encode(w, img, nil); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (cv *Converter) generateOutputPath(path string) string {
+	dirAndBase := strings.TrimRight(path, filepath.Ext(path))
+	ext := cv.imgFmtExts.ConvToExt(cv.fmtTo)
+	path = strings.Join([]string{dirAndBase, string(ext)}, ".")
+	return addOutputDir(path)
+}
+
+func addOutputDir(path string) string {
+	return strings.Join([]string{
+		"./output",
+		strings.TrimLeft(path, "./"),
+	}, "/")
+}
+
+// Detect specifies image format from file extension string.
+func (imgFmt *ImgFmt) Detect(cv *Converter, extStr string) {
+	ext := Ext(strings.ToLower(extStr))
+	*imgFmt = cv.imgFmtExts.ConvToImgFmt(ext)
+}
+
+// Match checks whether the file has an extension of the image format.
+func (imgFmt ImgFmt) Match(cv *Converter, fileName string) bool {
+	fileExtStr := strings.TrimPrefix(filepath.Ext(fileName), ".")
+	fileExt := Ext(strings.ToLower(fileExtStr))
+	fileImgFmt := cv.imgFmtExts.ConvToImgFmt(fileExt)
+	return fileImgFmt == imgFmt
+}
+
+// Init creates the map of image formats and its extensions available.
+func (m *MapImgFmtExts) Init() {
+	*m = MapImgFmtExts{
+		"jpeg": Exts{"jpg", "jpeg"},
+		"png":  Exts{"png"},
+		"gif":  Exts{"gif"},
+	}
+}
+
+// ConvToImgFmt converts image extension to its format.
+func (m MapImgFmtExts) ConvToImgFmt(ext Ext) ImgFmt {
+	for imgFmt, fmtExts := range m {
+		for _, fmtExt := range fmtExts {
+			if ext == fmtExt {
+				return imgFmt
+			}
+		}
+	}
+	return ""
+}
+
+// ConvToExt converts image format to its extension.
+func (m MapImgFmtExts) ConvToExt(imgFmt ImgFmt) Ext {
+	for keyImgFmt, fmtExts := range m {
+		if imgFmt == keyImgFmt {
+			return fmtExts[0]
+		}
+	}
+	return ""
+}