improve svg format detection (#135)

svg.go

@@ -9,14 +9,12 @@ import (
 func init() {
 	// Register fake svg decoder. Since we need this only for type detecting, we can
 	// return fake image sizes
-	image.RegisterFormat(
-		"svg",
-		"<?xml ",
-		func(io.Reader) (image.Image, error) {
-			return image.NewRGBA(image.Rect(0, 0, 1, 1)), nil
-		},
-		func(io.Reader) (image.Config, error) {
-			return image.Config{ColorModel: color.RGBAModel, Width: 1, Height: 1}, nil
-		},
-	)
+	decode := func(io.Reader) (image.Image, error) {
+		return image.NewRGBA(image.Rect(0, 0, 1, 1)), nil
+	}
+	decodeConfig := func(io.Reader) (image.Config, error) {
+		return image.Config{ColorModel: color.RGBAModel, Width: 1, Height: 1}, nil
+	}
+	image.RegisterFormat("svg", "<?xml ", decode, decodeConfig)
+	image.RegisterFormat("svg", "<svg", decode, decodeConfig)
 }