[pdiff] Check for too small images.

The Laplacian pyramid can only work on images larger than 3x3 due to the
size of its convolution kernel. So if the image is too small return an
error (-1) before attempting to construction the pyramid.

1 files changed, 3 insertions, 0 deletions

diff --git a/test/pdiff/pdiff.c b/test/pdiff/pdiff.c
index b75312dfe..4f3226db3 100644
--- a/test/pdiff/pdiff.c
+++ b/test/pdiff/pdiff.c
@@ -286,6 +286,9 @@ pdiff_compare (cairo_surface_t *surface_a,
 
     w = cairo_image_surface_get_width (surface_a);
     h = cairo_image_surface_get_height (surface_a);
+    if (w < 3 || h < 3) /* too small for the Laplacian convolution */
+	return -1;
+
     for (y = 0; y < h; y++) {
 	for (x = 0; x < w; x++) {
 	    float r, g, b, l;