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• Animation freezes after a number of frames after upgrading Matplotlib

  9 mars 2018, par Oliver von Baron

  I recently updated my matplotlib python package to version 2.2.0, and now some previously working code to save an animation does not work. Instead of saving an animation, the code freezes at a certain iteration number. It becomes unresponsive to interrupts and throws a PyEval_RestoreThread fatal error when I manage to close the command window.

  I am using Enthought Canopy. The code still works as normal with other versions of python and matplotlib.

  I can replicate the problem with this :

  import matplotlib.pyplot as plt
  
  import matplotlib.animation as animation
  
  import numpy as np
  
  
  
  SIZE = 128
  
  fig, ax = plt.subplots()
  
  
  
  ims = ax.imshow(np.random.rand(SIZE, SIZE))
  
  
  
  i = 0
  
  def update_animation(*args):
  
      global i
  
      i = i + 1
  
      image = np.random.rand(SIZE, SIZE)
  
      ims.set_data(image)
  
      print "Iteration "+str(i)
  
  
  
  F_NAME = "anim_test.mp4"
  
  NUM_ITERS = 1000
  
  FFwriter = animation.FFMpegWriter(fps=6, bitrate=500)
  
  anim=animation.FuncAnimation(fig,update_animation,frames=NUM_ITERS,blit=False, repeat=False, interval=200)
  
  anim.save(F_NAME, writer=FFwriter)    
  
  print "saved animation to " + F_NAME

  Changing the bitrate parameter changed the number of the frame the program halts at. For bitrate=500, it halts around frame 46.

  How can I stop pyplot freezing before all frames can be saved ?

  EDIT
  My system details :
  Python 2.7.6 64bit Enthought Canopy
  Windows 8
  8GB RAM
  ffmpeg version N-79075-ga7b8a6e

• Exception in Tkinter callback while saving animation with matplotlib

  24 août 2017, par paul

  I’m a little hesitant about asking this, since there seem to be many "Exception in Tkinter callback" questions, but I cannot find one that fits the problem I have here.

  I am trying to save an MP4 animation (of a percolation simulation) using matplotlib with ffmpeg. The code works fine on my home laptop, but not on my work PC. It also works fine if I replace the anim.save line with plt.show(), but I do want to save the animation. I’m using Python 3.5.2 on Ubuntu 17.04 (and I have ffmpeg installed).

  Here is the error :

  >>> Exception in Tkinter callback
  
  Traceback (most recent call last):
  
    File "/usr/lib/python3.5/tkinter/__init__.py", line 1558, in __call__
  
      return self.func(*args)
  
    File "/usr/lib/python3.5/tkinter/__init__.py", line 604, in callit
  
      func(*args)
  
    File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_tkagg.py", line 373, in idle_draw
  
      self.draw()
  
    File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_tkagg.py", line 354, in draw
  
      FigureCanvasAgg.draw(self)
  
    File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_agg.py", line 474, in draw
  
      self.figure.draw(self.renderer)
  
    File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 62, in draw_wrapper
  
      draw(artist, renderer, *args, **kwargs)
  
    File "/usr/lib/python3/dist-packages/matplotlib/figure.py", line 1165, in draw
  
      self.canvas.draw_event(renderer)
  
    File "/usr/lib/python3/dist-packages/matplotlib/backend_bases.py", line 1809, in draw_event
  
      self.callbacks.process(s, event)
  
    File "/usr/lib/python3/dist-packages/matplotlib/cbook.py", line 563, in process
  
      proxy(*args, **kwargs)
  
    File "/usr/lib/python3/dist-packages/matplotlib/cbook.py", line 430, in __call__
  
      return mtd(*args, **kwargs)
  
    File "/usr/lib/python3/dist-packages/matplotlib/animation.py", line 661, in _start
  
      self._init_draw()
  
    File "/usr/lib/python3/dist-packages/matplotlib/animation.py", line 1221, in _init_draw
  
      self._draw_frame(next(self.new_frame_seq()))
  
  StopIteration

  The code producing the error is :

  def percolate():
  
  
  
      # initialize an instance of the Percolator class
  
      perc = Percolator(1, 100, 0.1)
  
  
  
      # initialize the image
  
      fig, ax = plt.subplots()
  
      im = plt.imshow(perc.states)
  
  
  
      anim = animation.FuncAnimation(fig, perc.update, perc.update_iter, repeat=False, fargs=(im, ), save_count=perc.n**2)
  
      anim.save("perc.mp4")

  I can reproduce the code for the Percolator class if necessary, but that part is working fine. It has two functions : update_iter, a generator function that yields True as long as the animation should continue, and update, which takes (the result of the iterator and) im as inputs, and its last two lines are

  im.set_array(self.states)
  
  return im,

  UPDATE :

  Here’s an MWE.

  import numpy as np
  
  import matplotlib.pyplot as plt
  
  from matplotlib import animation
  
  
  
  
  
  class Percolator:
  
  
  
      def __init__(self):
  
          self.i = 0
  
          self.states = np.zeros((10, 10))
  
          self.end = False
  
  
  
      def update(self, garbage=None, im=None):
  
          self.i += 1
  
          if self.i == 10:
  
              self.end = True
  
          im.set_array(self.states)
  
          return im,
  
  
  
      def update_iter(self):
  
          while self.end == False:
  
              yield True
  
  
  
  def percolate():
  
  
  
      perc = Percolator()
  
      fig, ax = plt.subplots()
  
      im = plt.imshow(perc.states)
  
  
  
      anim = animation.FuncAnimation(fig, perc.update, perc.update_iter, repeat=False, \
  
                                     fargs=(im, ), save_count=100)
  
  
  
      anim.save("perc.gif", writer="imagemagick")

  In this example, the Percolator class doesn’t do anything interesting - it sets up a 10x10 grid of 0s, and each call to its update function sets the image to the same 10x10 grid.

  If the frames attribute of FuncAnimation is set to 50 (say), rather than to perc.update_iter, then there is no error and the image is saved correctly. So the problem seems to be with my generator function. I want to use the generator function because I want to keep creating new frames until some condition on perc.states is met - here, boringly, I’ve just asked it to keep going for 10 iterations.

  System details : Python 3.5.3, matplotlib 2.0.0, Ubuntu 17.04.

  UPDATE 2 :

  Same problem after upgrading to matplotlib 2.0.2. Also, printing some output along the way reveals that the error occurs at the end of the iterations. In fact, if update_iter is changed to :

  def update_iter(self):
  
      print(self.end)
  
      while self.end == False:
  
          yield True

  ... then the output is :

  False
  
  False
  
  False
  
  False
  
  False
  
  False
  
  False
  
  False
  
  False
  
  False
  
  False
  
  True
  
  >>> True
  
  Exception in Tkinter callback
  
  Traceback (most recent call last):
  
  etc.

• Matplotlib animation error : Requested MovieWriter (ffmpeg) not available, while ffmpeg is installed

  3 juillet 2020, par Vivien Bonnot

  I'm trying to animate colormapping representations of parametric complex fonctions using Python.
I gradually put some things together, and checked that they worked properly. But I can't get the animation to be saved.

  


  I encountered this error :

  


  Requested MovieWriter (ffmpeg) not available

  


  However, ffmpeg is indeed installed on my system,
on Windows console ffmpeg -version returns all sorts of informations about ffmpeg. Additionnaly, I also installed ffmpeg in Python scripts directory using pip pip install ffmpeg, which was successfull. I also set up ffmepg path in my code : plt.rcParams['animation.ffmpeg_path'] = "C:\FFmpeg\bin\ffmpeg.exe"

  


  I'm runing out of ideas.

  


  Here is my code.
Thank you for reading.

  


  import numpy as np
import math
import matplotlib
import matplotlib.pyplot as plt
import matplotlib.animation as animation
pi=math.pi
plt.rcParams['animation.ffmpeg_path'] = "C:\FFmpeg\bin\ffmpeg.exe"
fig = plt.figure()

def complex_array_to_rgb(X, theme='dark', rmax=None):
  absmax = rmax or np.abs(X).max()
  Y = np.zeros(X.shape + (3,), dtype='float')
  Y[..., 0] = np.angle(X) / (2 * pi) % 1
  if theme == 'light':
    Y[..., 1] = np.clip(np.abs(X) / absmax, 0, 1)
    Y[..., 2] = 1
  elif theme == 'dark':
    Y[..., 1] = 1
    Y[..., 2] = np.clip(np.abs(X) / absmax, 0, 1)
  Y = matplotlib.colors.hsv_to_rgb(Y)
  return Y

# Set up formatting for the movie files
Writer = animation.writers['ffmpeg']
writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)

fps = 10
nSeconds = 1
snapshots = [ complex_array_to_rgb(np.array([[3*(x + 1j*y)**(2.9+p/300) + 1/(x + 1j*y)**2 for x in np.arange(-1,1,0.05)] for y in np.arange(-1,1,0.05)])) for p in range( nSeconds * fps ) ]

fig = plt.figure( figsize=(3,3) )

Z2=snapshots[0]
im=plt.imshow(Z2, extent=(-1,1,-1,1))

def animate_func(i):
    if i % fps == 0:
        print( '.')

    im.set_array(snapshots[i])
    return [im]
    
anim = animation.FuncAnimation(
                               fig, 
                               animate_func, 
                               frames = nSeconds * fps,
                               interval = 1000 / fps, # in ms
                               )

anim.save('test_anim.mp4', writer=writer)