perf: convert_alpha() cached drawImage surfaces for faster blits

src/main/python/preponderous/graphik/graphik.py

@@ -111,7 +111,13 @@ def drawImage(self, filePath, xpos, ypos, width, height):
         # mid-run will not be picked up -- the normal tradeoff for a game
         # asset cache.
         if filePath not in self._images:
-            self._images[filePath] = pygame.image.load(filePath)
+            # convert_alpha() rebuilds the surface in the display's pixel
+            # format (and preserves any per-pixel alpha), which is what makes
+            # repeated blit() calls fast -- an unconverted surface is
+            # reformatted on every single blit. Doing it once here, alongside
+            # the load, keeps that cost out of the per-frame path this cache
+            # exists to protect.
+            self._images[filePath] = pygame.image.load(filePath).convert_alpha()
         image = self._images[filePath]
 
         size = (width, height)

src/test/python/preponderous/graphik/test_graphik.py

@@ -175,6 +175,26 @@ def test_draw_image_rescales_when_size_changes(monkeypatch, tmp_path):
     assert [args[1] for args in scaled] == [(10, 10), (12, 12), (10, 10)]
 
 
+def test_draw_image_converts_loaded_surface_for_faster_blits(monkeypatch, tmp_path):
+    # pygame.Surface is a builtin type (its methods can't be monkeypatched),
+    # so observe the conversion through the surface actually handed to
+    # transform.scale rather than spying on convert_alpha() directly.
+    graphik = _make_graphik()
+    image_path = tmp_path / "red.bmp"
+    _write_solid_image(image_path, (255, 0, 0))
+
+    rawImage = pygame.image.load(str(image_path))
+    scaled = _count_image_scales(monkeypatch)
+
+    graphik.drawImage(str(image_path), 0, 0, 10, 10)
+
+    sourcePassedToScale = scaled[0][0]
+    # convert_alpha() adds a per-pixel alpha channel that a plain BMP load
+    # does not have; its presence proves the cached surface was converted.
+    assert not rawImage.get_flags() & pygame.SRCALPHA
+    assert sourcePassedToScale.get_flags() & pygame.SRCALPHA
+
+
 def test_draw_image_still_blits_correctly_after_caching(tmp_path):
     pygame.display.init()
     display = pygame.display.set_mode((20, 20))