refactor(#55): minor changes, use proper declarations, unref image

image.go

@@ -4,6 +4,11 @@ type Image struct {
 	buffer []byte
 }
 
+// Creates a new image
+func NewImage(buf []byte) *Image {
+	return &Image{buf}
+}
+
 // Resize the image to fixed width and height
 func (i *Image) Resize(width, height int) ([]byte, error) {
 	options := Options{
@@ -190,8 +195,3 @@ func (i *Image) Size() (ImageSize, error) {
 func (i *Image) Image() []byte {
 	return i.buffer
 }
-
-// Creates a new image
-func NewImage(buf []byte) *Image {
-	return &Image{buf}
-}

options.go

@@ -80,6 +80,10 @@ type Color struct {
 	R, G, B uint8
 }
 
+// Shortcut to black RGB color representation
+var ColorBlack = Color{0, 0, 0}
+
+// Text-based watermark configuration
 type Watermark struct {
 	Width       int
 	DPI         int
@@ -96,6 +100,7 @@ type GaussianBlur struct {
 	MinAmpl float64
 }
 
+// Supported image transformation options
 type Options struct {
 	Height         int
 	Width          int
@@ -117,11 +122,11 @@ type Options struct {
 	NoProfile      bool
 	Interlace      bool
 	Rotate         Angle
+	Background     Color
 	Gravity        Gravity
 	Watermark      Watermark
 	Type           ImageType
 	Interpolator   Interpolator
 	Interpretation Interpretation
 	GaussianBlur   GaussianBlur
-	Background     Color
 }

resize.go

@@ -103,12 +103,9 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	}
 
 	// Flatten image on a background, if necessary
-	black := Color{0, 0, 0}
+	image, err = imageFlatten(image, imageType, o)
-	if imageType == PNG && o.Background != black {
+	if err != nil {
-		image, err = vipsFlatten(image, o.Background)
+		return nil, err
-		if err != nil {
-			return nil, err
-		}
 	}
 
 	saveOptions := vipsSaveOptions{
@@ -312,6 +309,15 @@ func watermakImage(image *C.VipsImage, w Watermark) (*C.VipsImage, error) {
 	return image, nil
 }
 
+func imageFlatten(image *C.VipsImage, imageType ImageType, o Options) (*C.VipsImage, error) {
+	// Only PNG images are supported for now
+	if imageType != PNG || o.Background == ColorBlack {
+		return image, nil
+	}
+
+	return vipsFlattenBackground(image, o.Background)
+}
+
 func zoomImage(image *C.VipsImage, zoom int) (*C.VipsImage, error) {
 	if zoom == 0 {
 		return image, nil

vips.go

@@ -252,14 +252,24 @@ func vipsInterpretation(image *C.VipsImage) Interpretation {
 	return Interpretation(C.vips_image_guess_interpretation_bridge(image))
 }
 
-func vipsFlatten(image *C.VipsImage, background Color) (*C.VipsImage, error) {
+func vipsFlattenBackground(image *C.VipsImage, background Color) (*C.VipsImage, error) {
 	var outImage *C.VipsImage
-	backgroundC := [3]C.double{C.double(background.R), C.double(background.G), C.double(background.B)}
+
-	err := int(C.vips_flatten_image(image, &outImage, (*C.double)(&backgroundC[0])))
+	backgroundC := [3]C.double{
-	if err != 0 {
+		C.double(background.R),
+		C.double(background.G),
+		C.double(background.B),
+	}
+
+	err := C.vips_flatten_background_brigde(image, &outImage, (*C.double)(&backgroundC[0]))
+	if int(err) != 0 {
 		return nil, catchVipsError()
 	}
-	return outImage, nil
+
+	C.g_object_unref(C.gpointer(image))
+	image = outImage
+
+	return image, nil
 }
 
 func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
@@ -277,8 +287,8 @@ func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
 	// Apply the proper colour space
 	var outImage *C.VipsImage
 	if vipsColourspaceIsSupported(image) {
-		err := int(C.vips_colourspace_bridge(image, &outImage, interpretation))
+		err := C.vips_colourspace_bridge(image, &outImage, interpretation)
-		if err != 0 {
+		if int(err) != 0 {
 			return nil, catchVipsError()
 		}
 		C.g_object_unref(C.gpointer(image))

vips.h

@@ -227,7 +227,7 @@ vips_webpsave_bridge(VipsImage *in, void **buf, size_t *len, int strip, int qual
 }
 
 int
-vips_flatten_image(VipsImage *in, VipsImage **out, double background[3]) {
+vips_flatten_background_brigde(VipsImage *in, VipsImage **out, double background[3]) {
 	VipsArrayDouble *vipsBackground = vips_array_double_new(background, 3);
 	return vips_flatten(in, out,
 		"background", vipsBackground,