+
+
package imgconv
+
+import (
+ "io"
+ "os"
+)
+
+type FileHandler interface {
+ Open(string) (io.ReadCloser, error)
+ Create(string) (io.WriteCloser, error)
+}
+
+type File struct{}
+
+func (File) Open(n string) (io.ReadCloser, error) { return os.Open(n) }
+func (File) Create(n string) (io.WriteCloser, error) { return os.Create(n) }
+
+func NewFile() File {
+ return File{}
+}
+
+
+
package imgconv
+
+import (
+ "image"
+ "image/gif"
+ "image/jpeg"
+ "image/png"
+ "io"
+
+ "golang.org/x/image/bmp"
+ "golang.org/x/image/tiff"
+)
+
+type Decoder interface {
+ Decode(io.Reader) (image.Image, error)
+}
+
+type Encoder interface {
+ Encode(io.Writer, image.Image) error
+}
+
+type ImageFormater interface {
+ Decoder
+ Encoder
+ GetExt() string
+}
+
+type ImageFormat struct {
+ Ext string
+}
+
+// ImagePng is type for png format.
+type PNG ImageFormat
+
+func (PNG) Decode(r io.Reader) (image.Image, error) { return png.Decode(r) }
+func (PNG) Encode(w io.Writer, i image.Image) error { return png.Encode(w, i) }
+func (p *PNG) GetExt() string { return p.Ext }
+
+// JPEG is type for jpeg format.
+type JPEG ImageFormat
+
+func (JPEG) Decode(r io.Reader) (image.Image, error) { return jpeg.Decode(r) }
+func (JPEG) Encode(w io.Writer, i image.Image) error { return jpeg.Encode(w, i, nil) }
+func (j *JPEG) GetExt() string { return j.Ext }
+
+// GIF is type for gif format.
+type GIF ImageFormat
+
+func (GIF) Decode(r io.Reader) (image.Image, error) { return gif.Decode(r) }
+func (GIF) Encode(w io.Writer, i image.Image) error {
+ return gif.Encode(w, i, &gif.Options{NumColors: 256})
+}
+func (g *GIF) GetExt() string { return g.Ext }
+
+// BMP is type for bmp format.
+type BMP ImageFormat
+
+func (BMP) Decode(r io.Reader) (image.Image, error) { return bmp.Decode(r) }
+func (BMP) Encode(w io.Writer, i image.Image) error { return bmp.Encode(w, i) }
+func (b *BMP) GetExt() string { return b.Ext }
+
+// TIFF is type for tiff format.
+type TIFF ImageFormat
+
+func (TIFF) Decode(r io.Reader) (image.Image, error) { return tiff.Decode(r) }
+func (TIFF) Encode(w io.Writer, i image.Image) error { return tiff.Encode(w, i, nil) }
+func (t *TIFF) GetExt() string { return t.Ext }
+
+func NewImageFormat(ext string) ImageFormater {
+ switch ext {
+ case "png":
+ return &PNG{Ext: ext}
+ case "jpg", "jpeg":
+ return &JPEG{Ext: ext}
+ case "gif":
+ return &GIF{Ext: ext}
+ case "bmp":
+ return &BMP{Ext: ext}
+ case "tiff", "tif":
+ return &TIFF{Ext: ext}
+ }
+
+ return nil
+}
+
+
+
// Imgconv package is to convert images file format.
+package imgconv
+
+import "io"
+
+// ConvertParam is parameter to convert image format.
+type ConvertParam struct {
+ Path string
+ FileHandler FileHandler
+ BeforeFormat ImageFormater
+ AfterFormat ImageFormater
+}
+
+// Do is func to convert image format.
+func Do(param ConvertParam) (rerr error) {
+ r, err := param.FileHandler.Open(param.Path)
+ if err != nil {
+ return err
+ }
+ defer r.Close()
+
+ n := buildAfterPath(param.Path, param.BeforeFormat.GetExt(), param.AfterFormat.GetExt())
+ w, err := param.FileHandler.Create(n)
+ if err != nil {
+ return err
+ }
+ defer func() {
+ err := w.Close()
+ if err != nil {
+ rerr = err
+ }
+ }()
+
+ if err := convert(r, param.BeforeFormat, w, param.AfterFormat); err != nil {
+ return err
+ }
+
+ return nil
+}
+
+func buildAfterPath(path, beforeExt, afterExt string) string {
+ e := len(path) - len(beforeExt)
+ return path[:e] + afterExt
+}
+
+func convert(r io.Reader, d Decoder, w io.Writer, e Encoder) error {
+ img, err := d.Decode(r)
+ if err != nil {
+ return err
+ }
+
+ if err := e.Encode(w, img); err != nil {
+ return err
+ }
+
+ return nil
+}
+
+
+