animationmatplotlibgif

matplotlib save animation in gif error


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.


Solution

  • 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)
    

    enter image description here