Merge pull request #6576 from radarhere/gif

Tests/test_file_gif.py

@@ -83,6 +83,21 @@ def test_l_mode_transparency():
         assert im.load()[0, 0] == 128
 
 
+def test_l_mode_after_rgb():
+    with Image.open("Tests/images/no_palette_after_rgb.gif") as im:
+        im.seek(1)
+        assert im.mode == "RGB"
+
+        im.seek(2)
+        assert im.mode == "RGB"
+
+
+def test_palette_not_needed_for_second_frame():
+    with Image.open("Tests/images/palette_not_needed_for_second_frame.gif") as im:
+        im.seek(1)
+        assert_image_similar(im, hopper("L").convert("RGB"), 8)
+
+
 def test_strategy():
     with Image.open("Tests/images/iss634.gif") as im:
         expected_rgb_always = im.convert("RGB")

src/PIL/GifImagePlugin.py

@@ -274,6 +274,8 @@ class GifImageFile(ImageFile.ImageFile):
                     p = self.fp.read(3 << bits)
                     if self._is_palette_needed(p):
                         palette = ImagePalette.raw("RGB", p)
+                    else:
+                        palette = False
 
                 # image data
                 bits = self.fp.read(1)[0]
@@ -298,7 +300,7 @@ class GifImageFile(ImageFile.ImageFile):
         if self.dispose:
             self.im.paste(self.dispose, self.dispose_extent)
 
-        self._frame_palette = palette or self.global_palette
+        self._frame_palette = palette if palette is not None else self.global_palette
         self._frame_transparency = frame_transparency
         if frame == 0:
             if self._frame_palette:
@@ -438,16 +440,13 @@ class GifImageFile(ImageFile.ImageFile):
                     self.mode = "RGB"
                 self.im = self.im.convert(self.mode, Image.Dither.FLOYDSTEINBERG)
             return
-        if self.mode == "P" and self._prev_im:
-            if self._frame_transparency is not None:
-                self.im.putpalettealpha(self._frame_transparency, 0)
-                frame_im = self.im.convert("RGBA")
-            else:
-                frame_im = self.im.convert("RGB")
+        if not self._prev_im:
+            return
+        if self._frame_transparency is not None:
+            self.im.putpalettealpha(self._frame_transparency, 0)
+            frame_im = self.im.convert("RGBA")
         else:
-            if not self._prev_im:
-                return
-            frame_im = self.im
+            frame_im = self.im.convert("RGB")
         frame_im = self._crop(frame_im, self.dispose_extent)
 
         self.im = self._prev_im