Add tests that transform functions keep palettes

Adds tests for two selected transform functions (scale and invert) to check some palette behavior, most importantly that the output surfaces have the same palettes as the input ones.

Author: Starbuck5

test/transform_test.py

@@ -173,6 +173,44 @@ def test_scale__alpha(self):
         self.assertEqual(s.get_alpha(), s3.get_alpha())
         self.assertEqual(s.get_alpha(), s2.get_alpha())
 
+    def test_scale__palette(self):
+        """see if palette information from source is kept.
+
+        Test for newsurf_fromsurf regression reported in
+        https://github.com/pygame-community/pygame-ce/issues/3463"""
+
+        s = pygame.Surface((32, 32), depth=8)
+        s.fill("red", [0, 0, 32, 16])
+        s.fill("purple", [0, 16, 32, 16])
+        self.assertTrue(len(s.get_palette()) > 0)
+
+        s2 = pygame.transform.scale(s, (64, 64))
+        self.assertEqual(s.get_palette()[0], s2.get_palette()[0])
+        self.assertEqual(s.get_at_mapped((0, 0)), s2.get_at_mapped((0, 0)))
+        self.assertEqual(s.get_at_mapped((0, 17)), s2.get_at_mapped((0, 35)))
+
+        # Also test with a custom palette to make sure the output doesn't just
+        # have a default palette.
+        s = pygame.Surface((32, 32), depth=8)
+        s.set_palette(
+            [
+                pygame.Color("red"),
+                pygame.Color("purple"),
+                pygame.Color("gold"),
+                pygame.Color("blue"),
+                pygame.Color("lightgreen"),
+            ]
+        )
+        s.fill("red", [0, 0, 32, 16])
+        s.fill("purple", [0, 16, 32, 16])
+        self.assertTrue(len(s.get_palette()) > 0)
+
+        s2 = pygame.transform.scale(s, (64, 64))
+        self.assertEqual(s.get_palette()[0], s2.get_palette()[0])
+        self.assertEqual(s.get_palette(), s2.get_palette())
+        self.assertEqual(s.get_at_mapped((0, 0)), s2.get_at_mapped((0, 0)))
+        self.assertEqual(s.get_at_mapped((0, 17)), s2.get_at_mapped((0, 35)))
+
     def test_scale__destination(self):
         """see if the destination surface can be passed in to use."""
 
@@ -1727,6 +1765,34 @@ def test_invert(self):
             pygame.Surface((10, 10), depth=8),
         )
 
+    def test_invert__palette(self):
+        """see if palette information from source is kept.
+
+        Test for newsurf_fromsurf regression reported in
+        https://github.com/pygame-community/pygame-ce/issues/3463"""
+
+        s = pygame.Surface((32, 32), depth=8)
+        s.set_palette([pygame.Color("orange") for _ in range(256)])
+        s.set_palette(
+            [
+                pygame.Color("red"),
+                pygame.Color("purple"),
+                pygame.Color("gold"),
+                pygame.Color("blue"),
+                pygame.Color("lightgreen"),
+            ]
+        )
+        s.fill("red", [0, 0, 32, 16])
+        s.fill("blue", [0, 16, 32, 16])
+        self.assertTrue(len(s.get_palette()) > 0)
+
+        s2 = pygame.transform.invert(s)
+        self.assertEqual(s.get_palette()[0], s2.get_palette()[0])
+        self.assertEqual(s.get_palette(), s2.get_palette())
+
+        self.assertEqual(s2.get_at((0, 0)), pygame.Color("lightgreen"))
+        self.assertEqual(s2.get_at((0, 17)), pygame.Color("gold"))
+
     def test_smoothscale(self):
         """Tests the stated boundaries, sizing, and color blending of smoothscale function"""
         # __doc__ (as of 2008-08-02) for pygame.transform.smoothscale: