问如何去除matplotlib动画中的压缩伪像？

EN

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation

images = np.array([
  np.tile(np.linspace(0, 1, 500), (50, 1)), 
  np.tile(np.linspace(1, 0, 500), (50, 1)), 
])
fps = 1

fig = plt.figure(frameon=False)
ax = plt.Axes(fig, [0., 0., 1., 1.])
fig.add_axes(ax)
artists = [[ax.imshow(image, animated=True, cmap='jet')] for image in images]
anim = animation.ArtistAnimation(fig, artists, interval=1000/fps, repeat_delay=1000)
writer = animation.PillowWriter(fps=fps, bitrate=500, codec="libx264", extra_args=['-pix_fmt', 'yuv420p'])
anim.save('./test_animation.gif', writer=writer)
ax.imshow(images[0], animated=True, cmap='jet');