Handle 16-bit PNGs

resize.go

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

@@ -55,6 +55,8 @@ type vipsSaveOptions struct {
 	Interlace      bool
 	NoProfile      bool
 	Interpretation Interpretation
+	Flatten        bool
+	Background     Color
 }
 
 type vipsWatermarkOptions struct {
@@ -341,6 +343,15 @@ 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

@@ -287,8 +287,7 @@ vips_flatten_background_brigde(VipsImage *in, VipsImage **out, double r, double
 	VipsArrayDouble *vipsBackground = vips_array_double_new(background, 3);
 
 	return vips_flatten(in, out,
-		"background", vipsBackground,
+		"background", vipsBackground, "max_alpha", 255.0,
-		"max_alpha", vips_is_16bit(in->Type) ? 65535.0 : 255.0,
 		NULL
 	);
 }