Fix failing tests on non-libpng backends

Author: ankith26

src_c/imageext.c

@@ -148,6 +148,18 @@ image_load_ext(PyObject *self, PyObject *arg, PyObject *kwarg)
         return RAISE(pgExc_SDLError, IMG_GetError());
     }
 
+    /* Vendor in fix from https://github.com/libsdl-org/SDL_image/pull/559.
+     * When that PR is merged this block can be removed. */
+    if (SDL_ISPIXELFORMAT_INDEXED(PG_SURF_FORMATENUM(surf)) &&
+        SDL_HasColorKey(surf)) {
+        Uint32 colorkey = -1;
+        SDL_GetColorKey(surf, &colorkey);
+        SDL_Palette *pal = PG_GetSurfacePalette(surf);
+        if (pal) {
+            pal->colors[colorkey].a = SDL_ALPHA_OPAQUE;
+        }
+    }
+
     final = (PyObject *)pgSurface_New(surf);
     if (final == NULL) {
         SDL_FreeSurface(surf);

test/image_test.py

@@ -203,6 +203,11 @@ def testSavePNG32(self):
         pygame.image.get_sdl_image_version() == (2, 0, 5),
         "SDL image 2.0.5 png saving will save this 24 bit as RGBA, causing reader.asRGB8 to fail",
     )
+    @unittest.skipIf(
+        "PG_DEPS_FROM_SYSTEM" in os.environ,
+        "If we are using system dependencies, we don't know the backend used "
+        "for PNG saving, and this test only works with libpng.",
+    )
     def testSavePNG24(self):
         """see if we can save a png with color values in the proper channels."""
         # Create a PNG file with known colors
@@ -238,6 +243,11 @@ def testSavePNG24(self):
             del reader
             os.remove(f_path)
 
+    @unittest.skipIf(
+        "PG_DEPS_FROM_SYSTEM" in os.environ,
+        "If we are using system dependencies, we don't know the backend used "
+        "for PNG saving, and this test only works with libpng.",
+    )
     def testSavePNG8(self):
         """see if we can save an 8 bit png correctly"""
         # Create an 8-bit PNG file with known colors

test/surface_test.py

@@ -1228,8 +1228,10 @@ def test_image_convert_bug_131(self):
             im = pygame.image.load(example_path(os.path.join("data", "city.png")))
             im2 = pygame.image.load(example_path(os.path.join("data", "brick.png")))
 
-            self.assertEqual(im.get_palette(), ((0, 0, 0, 255), (255, 255, 255, 255)))
-            self.assertEqual(im2.get_palette(), ((0, 0, 0, 255), (0, 0, 0, 255)))
+            self.assertEqual(
+                im.get_palette()[:2], ((0, 0, 0, 255), (255, 255, 255, 255))
+            )
+            self.assertEqual(im2.get_palette()[:2], ((0, 0, 0, 255), (0, 0, 0, 255)))
 
             self.assertEqual(
                 repr(im.convert(32)), "<Surface(24x24x32, colorkey=(0, 0, 0, 255))>"