Merge pull request #2902 from wiredfool/pr_2388

Add disposal option when saving GIFs

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:
@@ -503,15 +506,19 @@ def _write_local_header(fp, im, offset, flags):
         duration = int(im.encoderinfo["duration"] / 10)
     else:
         duration = 0
-    if transparent_color_exists or duration != 0:
-        transparency_flag = 1 if transparent_color_exists else 0
+
+    disposal = int(im.encoderinfo.get('disposal', 0))
+
+    if transparent_color_exists or duration != 0 or disposal:
+        packed_flag = 1 if transparent_color_exists else 0
+        packed_flag |= disposal << 2
         if not transparent_color_exists:
             transparency = 0
 
         fp.write(b"!" +
                  o8(249) +                # extension intro
                  o8(4) +                  # length
-                 o8(transparency_flag) +  # packed fields
+                 o8(packed_flag) +        # packed fields
                  o16(duration) +          # duration
                  o8(transparency) +       # transparency index
                  o8(0))

Tests/test_file_gif.py

@@ -259,6 +259,40 @@ class TestFileGif(PillowTestCase):
         except EOFError:
             pass
 
+    def test_save_dispose(self):
+        out = self.tempfile('temp.gif')
+        im_list = [
+            Image.new('L', (100, 100), '#000'),
+            Image.new('L', (100, 100), '#111'),
+            Image.new('L', (100, 100), '#222'),
+        ]
+        for method in range(0,4):
+            im_list[0].save(
+                out,
+                save_all=True,
+                append_images=im_list[1:],
+                disposal=method
+            )
+            img = Image.open(out)
+            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=tuple(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")
         # seek to the second frame

docs/handbook/image-file-formats.rst

@@ -132,6 +132,17 @@ are available::
     the palette can be passed in as an
     :py:class:`PIL.ImagePalette.ImagePalette` object.
 
+**disposal**
+    Indicates the way in which the graphic is to be treated after being displayed.
+
+    * 0 - No disposal specified.
+    * 1 - Do not dispose.
+    * 2 - Restore to background color.
+    * 3 - Restore to previous content.
+
+     Pass a single integer for a constant disposal, or a list or tuple
+     to set the disposal for each frame separately. 
+
 Reading local images
 ~~~~~~~~~~~~~~~~~~~~