Added per-frame disposal, tests

PIL/GifImagePlugin.py

@@ -392,6 +392,7 @@ def _write_single_frame(im, fp, palette):
 def _write_multiple_frames(im, fp, palette):
 
     duration = im.encoderinfo.get("duration", None)
+    disposal = im.encoderinfo.get('disposal', None)
 
     im_frames = []
     frame_count = 0
@@ -404,6 +405,8 @@ def _write_multiple_frames(im, fp, palette):
             encoderinfo = im.encoderinfo.copy()
             if isinstance(duration, (list, tuple)):
                 encoderinfo['duration'] = duration[frame_count]
+            if isinstance(disposal, (list, tuple)):
+                encoderinfo["disposal"] = disposal[frame_count]
             frame_count += 1
 
             if im_frames:

Tests/test_file_gif.py

@@ -274,12 +274,24 @@ class TestFileGif(PillowTestCase):
                 disposal=method
             )
             img = Image.open(out)
-            try:
-                while True:
-                    img.seek(img.tell() + 1)
-                    self.assertEqual(img.disposal_method, method)
-            except EOFError:
-                pass
+            for _ in range(2):
+                img.seek(img.tell() + 1)
+                self.assertEqual(img.disposal_method, method)
+
+
+        # check per frame disposal
+        im_list[0].save(
+            out,
+            save_all=True,
+            append_images=im_list[1:],
+            disposal=range(len(im_list))
+            )
+
+        img = Image.open(out)
+
+        for i in range(2):
+            img.seek(img.tell() + 1)
+            self.assertEqual(img.disposal_method, i+1)
 
     def test_iss634(self):
         img = Image.open("Tests/images/iss634.gif")