How can I make a video from array of images in mat

问题:

I have a couple of images that show how something changes in time. I visualize them as many images on the same plot with the following code:

import matplotlib.pyplot as plt
import matplotlib.cm as cm

img = [] # some array of images
fig = plt.figure()
for i in xrange(6):
    fig.add_subplot(2, 3, i + 1)
    plt.imshow(img[i], cmap=cm.Greys_r)

plt.show()

and get something like:

Which is ok, but I would rather animate them to get something like this video. How can I achieve this with python and preferably (not necessarily) with matplotlib

回答1:

For a future myself, here is what I ended up with:

def generate_video(img):
    for i in xrange(len(img)):
        plt.imshow(img[i], cmap=cm.Greys_r)
        plt.savefig(folder + "/file%02d.png" % i)

    os.chdir("your_folder")
    subprocess.call([
        'ffmpeg', '-framerate', '8', '-i', 'file%02d.png', '-r', '30', '-pix_fmt', 'yuv420p',
        'video_name.mp4'
    ])
    for file_name in glob.glob("*.png"):
        os.remove(file_name)

回答2:

You could for example export the images to png using plt.savefig("file%d.png" % i), then use ffmpeg to generate the video.

Here you find help to generate video from images

回答3:

I implemented a handy script that just suits you and new comers. Try it out here.

For your example:

imagelist = YOUR-IMAGE-LIST
def redraw_fn(f, axes):
    img = imagelist[f]
    if not redraw_fn.initialized:
        redraw_fn.im = axes.imshow(img, animated=True)
        redraw_fn.initialized = True
    else:
        redraw_fn.im.set_array(img)
redraw_fn.initialized = False

videofig(len(imagelist), redraw_fn, play_fps=30)

回答4:

Another solution is to use AnimationArtist from matplotlib.animation as described in the animated image demo. Adapting for your example would be

import matplotlib.pyplot as plt
import matplotlib.cm as cm

img = [] # some array of images
frames = [] # for storing the generated images
fig = plt.figure()
for i in xrange(6):
    frames.append([plt.imshow(img[i], cmap=cm.Greys_r,animated=True)])

ani = animation.ArtistAnimation(fig, ims, interval=50, blit=True,
                                repeat_delay=1000)
# ani.save('movie.mp4')
plt.show()