[Matplotlib-users] saving animations

[David P. <dj...@gm...>]

I am trying to save the frames from a matplotlib animation and I have a question that is undoubtedly based on a profound lack of understanding about how matplotlib/python works, but I'm hoping someone can offer me an explanation.  The following code is excerpted from the animation examples "animation_blit_wx.py".  The example works fine unless I include the #***** line meant to record the animations in included.  If the line is included, the animated line is no longer drawn to the screen or to the sequence of plots I am trying to save.  That is, the background is displayed and saved, but not the animated line.  Why?


def update_line(*args):
    global blit_time

    if update_line.background is None:
        update_line.background = canvas.copy_from_bbox(ax.bbox)

    # restore the clean slate background
    canvas.restore_region(update_line.background)
    # update the data
    line.set_ydata(npy.sin(x+update_line.cnt/10.0))
    # just draw the animated artist
    ax.draw_artist(line)
    # just redraw the axes rectangle

    t = time.time()
    canvas.blit(ax.bbox)
    blit_time += time.time() - t
    #***** plt.savefig('f' + str(update_line.cnt) + '.png') *****

    if update_line.cnt == NBLITS:
        # print the timing info and quit
        frame_time = time.time() - tstart
        print '%d frames: %.2f seconds' % (NBLITS, frame_time)
        print '%d blits:  %.2f seconds' % (NBLITS, blit_time)
        print
        print 'FPS: %.2f' % (NBLITS/frame_time)
        print 'BPS: %.2f' % (NBLITS/blit_time)
        sys.exit()

    update_line.cnt += 1
    wx.WakeUpIdle()