Added append_images parameter to GIF saving

PIL/GifImagePlugin.py

@@ -351,35 +351,38 @@ def _save(im, fp, filename, save_all=False):
         previous = None
 
         first_frame = None
-        for im_frame in ImageSequence.Iterator(im):
+        append_images = im.encoderinfo.get("append_images", [])
-            im_frame = _convert_mode(im_frame)
+        for imSequence in [im]+append_images:
+            for im_frame in ImageSequence.Iterator(imSequence):
+                encoderinfo = im.encoderinfo.copy()
+                im_frame = _convert_mode(im_frame)
 
-            # To specify duration, add the time in milliseconds to getdata(),
+                # To specify duration, add the time in milliseconds to getdata(),
-            # e.g. getdata(im_frame, duration=1000)
+                # e.g. getdata(im_frame, duration=1000)
-            if not previous:
+                if not previous:
-                # global header
+                    # global header
-                first_frame = getheader(im_frame, palette, im.encoderinfo)[0]
+                    first_frame = getheader(im_frame, palette, encoderinfo)[0]
-                first_frame += getdata(im_frame, (0, 0), **im.encoderinfo)
+                    first_frame += getdata(im_frame, (0, 0), **encoderinfo)
-            else:
-                if first_frame:
-                    for s in first_frame:
-                        fp.write(s)
-                    first_frame = None
-
-                # delta frame
-                delta = ImageChops.subtract_modulo(im_frame, previous.copy())
-                bbox = delta.getbbox()
-
-                if bbox:
-                    # compress difference
-                    encoderinfo['include_color_table'] = True
-                    for s in getdata(im_frame.crop(bbox),
-                                     bbox[:2], **im.encoderinfo):
-                        fp.write(s)
                 else:
-                    # FIXME: what should we do in this case?
+                    if first_frame:
-                    pass
+                        for s in first_frame:
-            previous = im_frame
+                            fp.write(s)
+                        first_frame = None
+
+                    # delta frame
+                    delta = ImageChops.subtract_modulo(im_frame, previous.copy())
+                    bbox = delta.getbbox()
+
+                    if bbox:
+                        # compress difference
+                        encoderinfo['include_color_table'] = True
+                        for s in getdata(im_frame.crop(bbox),
+                                         bbox[:2], **encoderinfo):
+                            fp.write(s)
+                    else:
+                        # FIXME: what should we do in this case?
+                        pass
+                previous = im_frame
         if first_frame:
             save_all = False
     if not save_all:

Tests/test_file_gif.py

@@ -306,6 +306,24 @@ class TestFileGif(PillowTestCase):
         reread = Image.open(out)
         self.assertEqual(reread.info["version"], b"GIF87a")
 
+    def test_append_images(self):
+        out = self.tempfile('temp.gif')
+
+        # Test appending single frame images
+        im = Image.new('RGB', (100, 100), '#f00')
+        ims = [Image.new('RGB', (100, 100), color) for color in ['#0f0', '#00f']]
+        im.save(out, save_all=True, append_images=ims)
+
+        reread = Image.open(out)
+        self.assertEqual(reread.n_frames, 3)
+
+        # Tests appending single and multiple frame images
+        im = Image.open("Tests/images/dispose_none.gif")
+        ims = [Image.open("Tests/images/dispose_prev.gif")]
+        im.save(out, save_all=True, append_images=ims)
+
+        reread = Image.open(out)
+        self.assertEqual(reread.n_frames, 10)
 
 if __name__ == '__main__':
     unittest.main()

docs/handbook/image-file-formats.rst

@@ -103,7 +103,9 @@ Saving sequences
 
 When calling :py:meth:`~PIL.Image.Image.save`, if a multiframe image is used,
 by default only the first frame will be saved. To save all frames, the
-``save_all`` parameter must be present and set to ``True``.
+``save_all`` parameter must be present and set to ``True``. To append
+additional frames when saving, the ``append_images`` parameter can be set to a
+list of images containing the extra frames.
 
 If present, the ``loop`` parameter can be used to set the number of times
 the GIF should loop, and the ``duration`` parameter can set the number of