Cleaner fix

resize.go

@@ -112,8 +112,11 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		return nil, err
 	}
 
-	// Only flatten PNG for now
-	flatten := imageType == PNG && o.Background != ColorBlack
+	// Flatten image on a background, if necessary
+	image, err = imageFlatten(image, imageType, o)
+	if err != nil {
+		return nil, err
+	}
 
 	saveOptions := vipsSaveOptions{
 		Quality:        o.Quality,
@@ -122,8 +125,6 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		Interlace:      o.Interlace,
 		NoProfile:      o.NoProfile,
 		Interpretation: o.Interpretation,
-		Flatten:        flatten,
-		Background:     o.Background,
 	}
 
 	// Finally get the resultant buffer
@@ -324,6 +325,14 @@ 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

@@ -55,8 +55,6 @@ type vipsSaveOptions struct {
 	Interlace      bool
 	NoProfile      bool
 	Interpretation Interpretation
-	Flatten        bool
-	Background     Color
 }
 
 type vipsWatermarkOptions struct {
@@ -343,15 +341,6 @@ func vipsPreSave(image *C.VipsImage, o *vipsSaveOptions) (*C.VipsImage, error) {
 		image = outImage
 	}
 
-	// Flatten image on a background, if necessary
-	if o.Flatten {
-		var err error
-		if outImage, err = vipsFlattenBackground(image, o.Background); err != nil {
-			return nil, err
-		}
-		image = outImage
-	}
-
 	return image, nil
 }
 

vips.h

@@ -283,11 +283,18 @@ vips_is_16bit (VipsInterpretation interpretation) {
 
 int
 vips_flatten_background_brigde(VipsImage *in, VipsImage **out, double r, double g, double b) {
+	if (vips_is_16bit(in->Type)) {
+		r = 65535 * r / 255;
+		g = 65535 * g / 255;
+		b = 65535 * b / 255;
+	}
+
 	double background[3] = {r, g, b};
 	VipsArrayDouble *vipsBackground = vips_array_double_new(background, 3);
 
 	return vips_flatten(in, out,
-		"background", vipsBackground, "max_alpha", 255.0,
+		"background", vipsBackground,
+		"max_alpha", vips_is_16bit(in->Type) ? 65535.0 : 255.0,
 		NULL
 	);
 }