matplotlib save animation in gif error

Question

I want to save matplotlib animation in gif format.

I succeded to save animation to mp4 format, using code

import matplotlib
matplotlib.use("Agg")

~some codes~

ani = animation.FuncAnimation(fig, draw, update, interval=10, blit=False)
mywriter = animation.FFMpegWriter(fps=60)
ani.save('myanimation.mp4',writer=mywriter)

but if I change myanimation.mp4 to gif format, python makes error

Traceback (most recent call last):
  File "C:\Users\Administrator\Desktop\edison\Edison_v4_backup_1\ver5.py", line 164, in <module>
    ani.save('demoanimation.gif',writer=mywriter);
  File "C:\Python27\lib\site-packages\matplotlib\animation.py", line 718, in save
    writer.grab_frame(**savefig_kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\animation.py", line 204, in grab_frame
    dpi=self.dpi, **savefig_kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\figure.py", line 1421, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\backend_bases.py", line 2220, in print_figure
    **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\backends\backend_agg.py", line 497, in print_raw
    renderer._renderer.write_rgba(filename_or_obj)
RuntimeError: Error writing to file

Seeing that I succeded to save in mp4 format, I don't know why it makes error when saving gif format.

Answer 1

This is because matplotlib does not support GIFs without external programs. If you have imagemagick correctly installed and configured, this should work:

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
import matplotlib.animation
import numpy as np


def init_animation():
    global line
    line, = ax.plot(x, np.zeros_like(x))
    ax.set_xlim(0, 2*np.pi)
    ax.set_ylim(-1,1)

def animate(i):
    line.set_ydata(np.sin(2*np.pi*i / 50)*np.sin(x))
    return line,

fig = plt.figure()
ax = fig.add_subplot(111)
x = np.linspace(0, 2*np.pi, 200)

ani = matplotlib.animation.FuncAnimation(fig, animate, init_func=init_animation, frames=50)
ani.save('/tmp/animation.gif', writer='imagemagick', fps=30)

Answer 2

Just a reminder, before you use Matplotlib and ImageMagick to convert images or videos to gif, you need to modify Matplotlib's config and add ImageMagick's path.

The following code will show you the config file path of Matplotlib

import matplotlib
matplotlib.matplotlib_fname()

For me the path is

C:\Anaconda\lib\site-packages\matplotlib\mpl-data\matplotlibrc

Then changing animation.convert_path

#animation.convert_path: 'convert' # Path to ImageMagick's convert binary.
                                   # On Windows use the full path since convert
                                   # is also the name of a system tool.

by adding convert.exe path to it

animation.convert_path: C:\Program Files\ImageMagick-6.9.2-Q16-HDRI\convert.exe

Don't forget to remove the # before animation.convert_path.

After the above modification, Matplotlib and ImageMagick will perfectly work and output the gif file you want.

Hope it helps.