fix(background): pass proper background RGB color

resize.go

@@ -330,7 +330,6 @@ func imageFlatten(image *C.VipsImage, imageType ImageType, o Options) (*C.VipsIm
 	if imageType != PNG || o.Background == ColorBlack {
 		return image, nil
 	}
-
 	return vipsFlattenBackground(image, o.Background)
 }
 

vips.go

@@ -304,7 +304,8 @@ func vipsFlattenBackground(image *C.VipsImage, background Color) (*C.VipsImage,
 	}
 
 	if vipsHasAlpha(image) {
-		err := C.vips_flatten_background_brigde(image, &outImage, (*C.double)(&backgroundC[0]))
+		err := C.vips_flatten_background_brigde(image, &outImage,
+			backgroundC[0], backgroundC[1], backgroundC[2])
 		if int(err) != 0 {
 			return nil, catchVipsError()
 		}

vips.h

@@ -277,12 +277,10 @@ vips_is_16bit (VipsInterpretation interpretation) {
 }
 
 int
-vips_flatten_background_brigde(VipsImage *in, VipsImage **out, double background[3]) {
-	background[0] *= 256;
-	background[1] *= 256;
-	background[2] *= 256;
-
+vips_flatten_background_brigde(VipsImage *in, VipsImage **out, double r, double g, double b) {
+	double background[3] = {r, g, b};
 	VipsArrayDouble *vipsBackground = vips_array_double_new(background, 3);
+	
 	return vips_flatten(in, out,
 		"background", vipsBackground,
 		"max_alpha", vips_is_16bit(in->Type) ? 65535.0 : 255.0,