Use previous disposal method in load_end

Tests/test_file_gif.py

@@ -307,6 +307,20 @@ def test_dispose_none():
             pass
 
 
+def test_dispose_none_load_end():
+    # Test image created with:
+    #
+    # im = Image.open("transparent.gif")
+    # im_rotated = im.rotate(180)
+    # im.save("dispose_none_load_end.gif",
+    #         save_all=True, append_images=[im_rotated], disposal=[1,2])
+    with Image.open("Tests/images/dispose_none_load_end.gif") as img:
+        img.seek(1)
+
+        with Image.open("Tests/images/dispose_none_load_end_second.gif") as expected:
+            assert_image_equal(img, expected)
+
+
 def test_dispose_background():
     with Image.open("Tests/images/dispose_bgnd.gif") as img:
         try:

src/PIL/GifImagePlugin.py

@@ -301,13 +301,14 @@ class GifImageFile(ImageFile.ImageFile):
 
         # if the disposal method is 'do not dispose', transparent
         # pixels should show the content of the previous frame
-        if self._prev_im and self.disposal_method == 1:
+        if self._prev_im and self._prev_disposal_method == 1:
             # we do this by pasting the updated area onto the previous
             # frame which we then use as the current image content
             updated = self._crop(self.im, self.dispose_extent)
             self._prev_im.paste(updated, self.dispose_extent, updated.convert("RGBA"))
             self.im = self._prev_im
         self._prev_im = self.im.copy()
+        self._prev_disposal_method = self.disposal_method
 
     def _close__fp(self):
         try: