Merge pull request #8253 from ngoldbaum/simplify-figsize-adjust

efiring · web-flow · commit 44fcb87dc9f1 · 2017-04-03T12:48:30.000-10:00
Handle floating point round-off error when converting to pixels for h264 animations
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -23,6 +23,7 @@
 import six
 from six.moves import xrange, zip
 
+import numpy as np
 import os
 import platform
 import sys
@@ -62,9 +63,38 @@
 
 
 def adjusted_figsize(w, h, dpi, n):
+    '''Compute figure size so that pixels are a multiple of n
+
+    Parameters
+    ----------
+    w, h : float
+        Size in inches
+
+    dpi : float
+        The dpi
+
+    n : int
+        The target multiple
+
+    Returns
+    -------
+    wnew, hnew : float
+        The new figure size in inches.
+    '''
+
+    # this maybe simplified if / when we adopt consistent rounding for
+    # pixel size across the whole library
+    def correct_roundoff(x, dpi, n):
+        if int(x*dpi) % n != 0:
+            if int(np.nextafter(x, np.inf)*dpi) % n == 0:
+                x = np.nextafter(x, np.inf)
+            elif int(np.nextafter(x, -np.inf)*dpi) % n == 0:
+                x = np.nextafter(x, -np.inf)
+        return x
+
     wnew = int(w * dpi / n) * n / dpi
     hnew = int(h * dpi / n) * n / dpi
-    return wnew, hnew
+    return (correct_roundoff(wnew, dpi, n), correct_roundoff(hnew, dpi, n))
 
 
 # A registry for available MovieWriter classes
@@ -278,8 +308,11 @@ def _adjust_frame_size(self):
                 verbose.report('figure size (inches) has been adjusted '
                                'from %s x %s to %s x %s' % (wo, ho, w, h),
                                level='helpful')
+        else:
+            w, h = self.fig.get_size_inches()
         verbose.report('frame size in pixels is %s x %s' % self.frame_size,
                        level='debug')
+        return w, h
 
     def setup(self, fig, outfile, dpi=None):
         '''
@@ -301,7 +334,7 @@ def setup(self, fig, outfile, dpi=None):
         if dpi is None:
             dpi = self.fig.dpi
         self.dpi = dpi
-        self._adjust_frame_size()
+        self._w, self._h = self._adjust_frame_size()
 
         # Run here so that grab_frame() can write the data to a pipe. This
         # eliminates the need for temp files.
@@ -337,6 +370,10 @@ def grab_frame(self, **savefig_kwargs):
         verbose.report('MovieWriter.grab_frame: Grabbing frame.',
                        level='debug')
         try:
+            # re-adjust the figure size in case it has been changed by the
+            # user.  We must ensure that every frame is the same size or
+            # the movie will not save correctly.
+            self.fig.set_size_inches(self._w, self._h)
             # Tell the figure to save its data to the sink, using the
             # frame format and dpi.
             self.fig.savefig(self._frame_sink(), format=self.frame_format,
@@ -386,16 +423,21 @@ def isAvailable(cls):
         if not bin_path:
             return False
         try:
-            p = subprocess.Popen(bin_path,
-                             shell=False,
-                             stdout=subprocess.PIPE,
-                             stderr=subprocess.PIPE,
-                             creationflags=subprocess_creation_flags)
-            p.communicate()
-            return True
+            p = subprocess.Popen(
+                bin_path,
+                shell=False,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                creationflags=subprocess_creation_flags)
+            return cls._handle_subprocess(p)
         except OSError:
             return False
 
+    @classmethod
+    def _handle_subprocess(cls, process):
+        process.communicate()
+        return True
+
 
 class FileMovieWriter(MovieWriter):
     '''`MovieWriter` for writing to individual files and stitching at the end.
@@ -570,10 +612,18 @@ def output_args(self):
 
         return args + ['-y', self.outfile]
 
+    @classmethod
+    def _handle_subprocess(cls, process):
+        _, err = process.communicate()
+        # Ubuntu 12.04 ships a broken ffmpeg binary which we shouldn't use
+        if 'Libav' in err.decode():
+            return False
+        return True
+
 
 # Combine FFMpeg options with pipe-based writing
 @writers.register('ffmpeg')
-class FFMpegWriter(MovieWriter, FFMpegBase):
+class FFMpegWriter(FFMpegBase, MovieWriter):
     '''Pipe-based ffmpeg writer.
 
     Frames are streamed directly to ffmpeg via a pipe and written in a single
@@ -594,7 +644,7 @@ def _args(self):
 
 # Combine FFMpeg options with temp file-based writing
 @writers.register('ffmpeg_file')
-class FFMpegFileWriter(FileMovieWriter, FFMpegBase):
+class FFMpegFileWriter(FFMpegBase, FileMovieWriter):
     '''File-based ffmpeg writer.
 
     Frames are written to temporary files on disk and then stitched
diff --git a/lib/matplotlib/tests/test_animation.py b/lib/matplotlib/tests/test_animation.py
@@ -145,6 +145,14 @@ def test_save_animation_smoketest(tmpdir, writer, extension):
     ax.set_xlim(0, 10)
     ax.set_ylim(-1, 1)
 
+    dpi = None
+    codec = None
+    if writer == 'ffmpeg':
+        # Issue #8253
+        fig.set_size_inches((10.85, 9.21))
+        dpi = 100.
+        codec = 'h264'
+
     def init():
         line.set_data([], [])
         return line,
@@ -160,7 +168,8 @@ def animate(i):
     with tmpdir.as_cwd():
         anim = animation.FuncAnimation(fig, animate, init_func=init, frames=5)
         try:
-            anim.save('movie.' + extension, fps=30, writer=writer, bitrate=500)
+            anim.save('movie.' + extension, fps=30, writer=writer, bitrate=500,
+                      dpi=dpi, codec=codec)
         except UnicodeDecodeError:
             pytest.xfail("There can be errors in the numpy import stack, "
                          "see issues #1891 and #2679")
