Fixed loading L mode GIF with transparency

python-pillow · Feb 24, 2022 · 1c85d44 · 1c85d44
1 parent 14b9b59
commit 1c85d44
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Showing 3 changed files with 23 additions and 4 deletions.
diff --git a/Tests/images/no_palette_with_transparency.gif b/Tests/images/no_palette_with_transparency.gif
diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
@@ -59,6 +59,17 @@ def test_invalid_file():
         GifImagePlugin.GifImageFile(invalid_file)
 
 
+def test_l_mode_transparency():
+    with Image.open("Tests/images/no_palette_with_transparency.gif") as im:
+        assert im.mode == "L"
+        assert im.load()[0, 0] == 0
+        assert im.info["transparency"] == 255
+
+        im.seek(1)
+        assert im.mode == "RGBA"
+        assert im.load()[0, 0] == (0, 0, 0, 255)
+
+
 def test_optimize():
     def test_grayscale(optimize):
         im = Image.new("L", (1, 1), 0)

diff --git a/src/PIL/GifImagePlugin.py b/src/PIL/GifImagePlugin.py
@@ -167,9 +167,14 @@ def _seek(self, frame):
         if self.__frame == 1:
             self.pyaccess = None
             if "transparency" in self.info:
+                if self.mode == "P":
+                    self.im.putpalettealpha(self.info["transparency"], 0)
+                    self.im = self.im.convert("RGBA", Image.Dither.FLOYDSTEINBERG)
+                else:
+                    self.im = self.im.convert_transparent(
+                        "RGBA", self.info["transparency"]
+                    )
                 self.mode = "RGBA"
-                self.im.putpalettealpha(self.info["transparency"], 0)
-                self.im = self.im.convert("RGBA", Image.Dither.FLOYDSTEINBERG)
 
                 del self.info["transparency"]
             else:
@@ -368,8 +373,11 @@ def load_end(self):
         if self.__frame == 0:
             return
         if self._frame_transparency is not None:
-            self.im.putpalettealpha(self._frame_transparency, 0)
-            frame_im = self.im.convert("RGBA")
+            if self.mode == "P":
+                self.im.putpalettealpha(self._frame_transparency, 0)
+                frame_im = self.im.convert("RGBA")
+            else:
+                frame_im = self.im.convert_transparent("RGBA", self._frame_transparency)
         else:
             frame_im = self.im.convert("RGB")
         frame_im = self._crop(frame_im, self.dispose_extent)