Backport PR #18093: Improve saving animated GIF with ffmpeg

tacaswell · meeseeksmachine · commit c8d1f6ed6a62 · 2020-07-29T03:14:27.000Z
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -310,7 +310,8 @@ def __init__(self, fps=5, codec=None, bitrate=None, extra_args=None,
                 'MovieWriter cannot be instantiated directly. Please use one '
                 'of its subclasses.')
 
-        super().__init__(fps=fps, metadata=metadata)
+        super().__init__(fps=fps, metadata=metadata, codec=codec,
+                         bitrate=bitrate)
 
         self.frame_format = 'rgba'
         self.extra_args = extra_args
@@ -571,7 +572,9 @@ class FFMpegBase:
     @property
     def output_args(self):
         args = []
-        if not Path(self.outfile).suffix == '.gif':
+        if Path(self.outfile).suffix == '.gif':
+            self.codec = 'gif'
+        else:
             args.extend(['-vcodec', self.codec])
         extra_args = (self.extra_args if self.extra_args is not None
                       else mpl.rcParams[self._args_key])
@@ -581,6 +584,11 @@ def output_args(self):
         # OSX). Also fixes internet explorer. This is as of 2015/10/29.
         if self.codec == 'h264' and '-pix_fmt' not in extra_args:
             args.extend(['-pix_fmt', 'yuv420p'])
+        # For GIF, we're telling FFMPEG to split the video stream, to generate
+        # a palette, and then use it for encoding.
+        elif self.codec == 'gif' and '-filter_complex' not in extra_args:
+            args.extend(['-filter_complex',
+                         'split [a][b];[a] palettegen [p];[b][p] paletteuse'])
         if self.bitrate > 0:
             args.extend(['-b', '%dk' % self.bitrate])  # %dk: bitrate in kbps.
         args.extend(extra_args)
