Add auto fixing jpg file orientation.

go/images/resizing.go

@@ -0,0 +1,36 @@
+package images
+
+import (
+	"bytes"
+	"github.com/disintegration/imaging"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+)
+
+func Resized(ext string, data []byte, width, height int) (resized []byte) {
+	if width == 0 && height == 0 {
+		return data
+	}
+	if srcImage, _, err := image.Decode(bytes.NewReader(data)); err == nil {
+		bounds := srcImage.Bounds()
+		var dstImage *image.NRGBA
+		if width == height && bounds.Dx() != bounds.Dy() {
+			dstImage = imaging.Thumbnail(srcImage, width, height, imaging.Lanczos)
+		} else {
+			dstImage = imaging.Resize(srcImage, width, height, imaging.Lanczos)
+		}
+		var buf bytes.Buffer
+		switch ext {
+		case ".png":
+			png.Encode(&buf, dstImage)
+		case ".jpg":
+			jpeg.Encode(&buf, dstImage, nil)
+		case ".gif":
+			gif.Encode(&buf, dstImage, nil)
+		}
+		return buf.Bytes()
+	}
+	return data
+}