Merge pull request #2852 from Damus666/blur-handle-zero-size-surfaces

Using blur on a surface with either width or height equal to 0 won't raise a ValueError

Author: oddbookworm

docs/reST/ref/transform.rst

@@ -245,6 +245,9 @@ Instead, always begin with the original image and scale to the desired size.)
    .. versionchanged:: 2.3.0
       Passing the calling surface as destination surface raises a ``ValueError``
 
+   .. versionchanged:: 2.5.0
+      A surface with either width or height equal to 0 won't raise a ``ValueError``
+
    .. ## pygame.transform.box_blur ##
 
 .. function:: gaussian_blur
@@ -271,6 +274,9 @@ Instead, always begin with the original image and scale to the desired size.)
       Now the standard deviation of the Gaussian kernel is equal to the radius. 
       Blur results will be slightly different.
 
+   .. versionchanged:: 2.5.0
+      A surface with either width or height equal to 0 won't raise a ``ValueError``
+
    .. ## pygame.transform.gaussian_blur ##
 
 .. function:: average_surfaces

src_c/transform.c

@@ -3266,6 +3266,15 @@ blur(pgSurfaceObject *srcobj, pgSurfaceObject *dstobj, int radius,
         retsurf = pgSurface_AsSurface(dstobj);
     }
 
+    if ((retsurf->w) != (src->w) || (retsurf->h) != (src->h)) {
+        return RAISE(PyExc_ValueError,
+                     "Destination surface not the same size.");
+    }
+
+    if (retsurf->w == 0 || retsurf->h == 0) {
+        return retsurf;
+    }
+
     Uint8 *ret_start = retsurf->pixels;
     Uint8 *ret_end = ret_start + retsurf->h * retsurf->pitch;
     Uint8 *src_start = src->pixels;
@@ -3279,11 +3288,6 @@ blur(pgSurfaceObject *srcobj, pgSurfaceObject *dstobj, int radius,
             "of them is a subsurface, or they are sharing the same buffer.");
     }
 
-    if ((retsurf->w) != (src->w) || (retsurf->h) != (src->h)) {
-        return RAISE(PyExc_ValueError,
-                     "Destination surface not the same size.");
-    }
-
     if (PG_SURF_BytesPerPixel(src) != PG_SURF_BytesPerPixel(retsurf)) {
         return (SDL_Surface *)(RAISE(
             PyExc_ValueError,

test/transform_test.py

@@ -1600,6 +1600,19 @@ def test_gaussian_blur(self):
         for pos in data2:
             self.assertTrue(sf_b2.get_at(pos) == data2[pos])
 
+    def test_blur_zero_size_surface(self):
+        surface = pygame.Surface((0, 0))
+        self.assertEqual(pygame.transform.box_blur(surface, 3).get_size(), (0, 0))
+        self.assertEqual(pygame.transform.gaussian_blur(surface, 3).get_size(), (0, 0))
+
+        surface = pygame.Surface((20, 0))
+        self.assertEqual(pygame.transform.box_blur(surface, 3).get_size(), (20, 0))
+        self.assertEqual(pygame.transform.gaussian_blur(surface, 3).get_size(), (20, 0))
+
+        surface = pygame.Surface((0, 20))
+        self.assertEqual(pygame.transform.box_blur(surface, 3).get_size(), (0, 20))
+        self.assertEqual(pygame.transform.gaussian_blur(surface, 3).get_size(), (0, 20))
+
     def test_flip(self):
         """honors the set_color key on the returned surface from flip."""
         image_loaded = pygame.image.load(example_path("data/chimp.png"))