add a convenient function to preprocess images on client side.

go/images/preprocess.go

@@ -0,0 +1,25 @@
+package images
+
+import (
+	"path/filepath"
+)
+
+/*
+* Preprocess image files on client side.
+* 1. possibly adjust the orientation
+* 2. resize the image to a width or height limit
+* 3. remove the exif data
+* Call this function on any file uploaded to weedfs
+* 
+*/
+func MaybePreprocessImage(filename string, data []byte, width, height int) (resized []byte) {
+	ext := filepath.Ext(filename)
+	switch ext {
+	case ".png", ".gif":
+		return Resized(ext, data, width, height)
+	case ".jpg", ".jpeg":
+	  data = FixJpgOrientation(data)
+		return Resized(ext, data, width, height)
+	}
+	return data
+}

go/images/resizing.go

@@ -25,7 +25,7 @@ func Resized(ext string, data []byte, width, height int) (resized []byte) {
 		switch ext {
 		case ".png":
 			png.Encode(&buf, dstImage)
-		case ".jpg":
+		case ".jpg", ".jpeg":
 			jpeg.Encode(&buf, dstImage, nil)
 		case ".gif":
 			gif.Encode(&buf, dstImage, nil)