Fix for memory issue when watermarking images

resize.go

@@ -354,13 +354,7 @@ func watermarkImageWithAnotherImage(image *C.VipsImage, w WatermarkImage) (*C.Vi
 		w.Opacity = 1.0
 	}
 
-	watermark, _, err := loadImage(w.Buf)
+	image, err := vipsDrawWatermark(image, w)
-
-	if err != nil {
-		return nil, err
-	}
-
-	image, err = vipsDrawWatermark(image, watermark, w)
 
 	if err != nil {
 		return nil, err

vips.go

@@ -596,16 +596,16 @@ func max(x int) int {
 	return int(math.Max(float64(x), 0))
 }
 
-func vipsDrawWatermark(image *C.VipsImage, watermark *C.VipsImage, o WatermarkImage) (*C.VipsImage, error) {
+func vipsDrawWatermark(image *C.VipsImage, o WatermarkImage) (*C.VipsImage, error) {
 	var out *C.VipsImage
 
-	if !vipsHasAlpha(image) {
+	watermark, _, e := vipsRead(o.Buf)
-		C.vips_add_band(image, &image, C.double(255.0))
+	if e != nil {
+		return nil, e
 	}
 
-	if !vipsHasAlpha(watermark) {
+	defer C.g_object_unref(C.gpointer(image))
-		C.vips_add_band(watermark, &watermark, C.double(255.0))
+	defer C.g_object_unref(C.gpointer(watermark))
-	}
 
 	opts := vipsWatermarkImageOptions{C.int(o.Left), C.int(o.Top), C.float(o.Opacity)}
 

vips.h

@@ -463,108 +463,42 @@ vips_add_band(VipsImage *in, VipsImage **out, double c) {
 
 int
 vips_watermark_image(VipsImage *in, VipsImage *sub, VipsImage **out, WatermarkImageOptions *o) {
-    int bands = in->Bands;
-    double background[4] = {0.0, 0.0, 0.0, 0.0};
-
-    VipsArrayDouble *vipsBackground = vips_array_double_new(background, 4);
-
 	VipsImage *base = vips_image_new();
-    VipsImage **t = (VipsImage **) vips_object_local_array(VIPS_OBJECT(base), 10);
+	VipsImage **t = (VipsImage **) vips_object_local_array(VIPS_OBJECT(base), 8);
 
 	t[0] = in;
 	t[1] = sub;
 
-    if (vips_embed(t[1], &t[2], o->Left, o->Top, t[0]->Xsize, t[0]->Ysize, "extend", VIPS_EXTEND_BACKGROUND, "background", vipsBackground, NULL)) {
+  if (has_alpha_channel(in) == 0) {
-        g_object_unref(base);
+		vips_bandjoin_const1(in, &t[0], 255.0, NULL);
-    	return 1;
 	}
 
-    //Get Sub bands without alpha
+	if (has_alpha_channel(sub) == 0) {
-    if (vips_extract_band(t[2], &t[3], 0, "n", t[2]->Bands - 1, NULL)) {
+		vips_bandjoin_const1(sub, &t[1], 255.0, NULL);
-        g_object_unref(base);
-    	return 1;
 	}
 
-    //Get Sub Image alpha
+	// Place watermark image in the right place and size it to the size of the
+	// image that should be watermarked
 	if (
-        vips_extract_band(t[2], &t[4], t[2]->Bands - 1, "n", 1, NULL) ||
+		vips_embed(t[1], &t[2], o->Left, o->Top, t[0]->Xsize, t[0]->Ysize, NULL)) {
-        vips_linear1(t[4], &t[4], o->Opacity / 255.0, 0.0, NULL)
-    ) {
-        g_object_unref(base);
-        return 1;
-    }
-
-    //Apply alpha to other sub bands to remove unwanted pixels
-    if (vips_multiply(t[3], t[4], &t[3], NULL)) {
-        g_object_unref(base);
-        return 1;
-    }
-
-    //Get in bands without alpha
-    if (vips_extract_band(t[0], &t[5], 0, "n", t[0]->Bands - 1, NULL)) {
 			g_object_unref(base);
 		return 1;
 	}
 
-    //Get in alpha
+	// Create a mask image based on the alpha band from the watermark image
+	// and place it in the right position
 	if (
-        vips_extract_band(t[0], &t[6], t[0]->Bands - 1, "n", 1, NULL) ||
+		vips_extract_band(t[1], &t[3], t[1]->Bands - 1, "n", 1, NULL) ||
-        vips_linear1(t[6], &t[6], 1.0 / 255.0, 0.0, NULL)
+		vips_linear1(t[3], &t[4], o->Opacity, 0.0, NULL) ||
-    ) {
+		vips_cast(t[4], &t[5], VIPS_FORMAT_UCHAR, NULL) ||
+		vips_copy(t[5], &t[6], "interpretation", t[0]->Type, NULL) ||
+		vips_embed(t[6], &t[7], o->Left, o->Top, t[0]->Xsize, t[0]->Ysize, NULL))	{
 			g_object_unref(base);
 		return 1;
 	}
 
-
+	// Blend the mask and watermark image and write to output.
-    // Compute normalized output alpha channel:
+	if (vips_ifthenelse(t[7], t[2], t[0], out, "blend", TRUE, NULL)) {
-    //
-    // References:
-    // - http://en.wikipedia.org/wiki/Alpha_compositing#Alpha_blending
-    // - https://github.com/jcupitt/ruby-vips/issues/28#issuecomment-9014826
-    //
-    // out_a = src_a + dst_a * (1 - src_a)
-    //                         ^^^^^^^^^^^
-
-    if (
-        vips_linear1(t[4], &t[7], -1.0, 1.0, NULL) ||
-        vips_multiply(t[6], t[7], &t[8], NULL)
-    ) {
-        g_object_unref(base);
-        return 1;
-    }
-
-    //outAlphaNormalized in t[8]
-    if (vips_add(t[4], t[8], &t[8], NULL)) {
-        g_object_unref(base);
-        return 1;
-    }
-
-    // Compute output RGB channels:
-    //
-    // Wikipedia:
-    // out_rgb = (src_rgb * src_a + dst_rgb * dst_a * (1 - src_a)) / out_a
-    //                                                ^^^^^^^^^^^
-    //                                                    t0
-    //
-    // Omit division by `out_a` since `Compose` is supposed to output a
-    // premultiplied RGBA image as reversal of premultiplication is handled
-    // externally.
-
-    if (vips_multiply(t[5], t[7], &t[9], NULL)) {
-         g_object_unref(base);
-         return 1;
-    }
-
-    //outRGBPremultiplied in t[9]
-    if (vips_add(t[3], t[9], &t[9], NULL)) {
-         g_object_unref(base);
-         return 1;
-    }
-
-    if (
-        vips_linear1(t[8], &t[8], 255.0, 0.0, NULL) ||
-        vips_bandjoin2(t[9], t[8], out, NULL)
-    ) {
 		g_object_unref(base);
 		return 1;
 	}

vips_test.go

@@ -123,10 +123,10 @@ func TestVipsWatermark(t *testing.T) {
 func TestVipsWatermarkWithImage(t *testing.T) {
 	image, _, _ := vipsRead(readImage("test.jpg"))
 
-	watermark, _, _ := vipsRead(readImage("transparent.png"))
+	watermark := readImage("transparent.png")
 
-	options := WatermarkImage{Left: 100, Top: 100, Opacity: 1.0}
+	options := WatermarkImage{Left: 100, Top: 100, Opacity: 1.0, Buf: watermark}
-	newImg, err := vipsDrawWatermark(image, watermark, options)
+	newImg, err := vipsDrawWatermark(image, options)
 	if err != nil {
 		t.Errorf("Cannot add watermark: %s", err)
 	}