Creating an animation out of Matplotlib .pngs

Question

Hello I just finished to write a code that compute the orbitals of the hydrogen atom. I wrote a for loop to create 300 pictures using the command

plt.savefig("image{i}.png".format(i=i))

Now I wanted to ask what is the easiest way to create a high quality .mp4 or .gif file out of the pictures using python. I saw several tutorials that didn't helped me because the gif was messed up or the quality was too low.

Thank you for your support

bit broad - what did you try? I successfully did animations using GIMP 2 but to an animated gif. There are plenty of aproaches using ffmpeg: https://stackoverflow.com/questions/24961127/how-to-create-a-video-from-images-with-ffmpeg and threads for python like this: [python-make-a-video-using-several-png-images](https://stackoverflow.com/questions/13590976/python-make-a-video-using-several-png-images) — Patrick Artner, May 10 '20 at 17:37

score 2 · Answer 1 · answered May 10 '20 at 17:37

2

The easiest I know is to use imageio's mimwrite.

import imageio
ims = [imageio.imread(f) for f in list_of_im_paths]
imageio.mimwrite(path_to_save_gif, ims)

There are obvious options such as duration, number of loops, etc.
And some other options you can read about in the documentation by using imageio.help('gif').

Hope that helps.

answered May 10 '20 at 17:37

ShlomiF

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I changed list_of_im_paths to "~/Plot" the directory where the .png are saved but I get a syntax error. – Phicalc May 10 '20 at 17:59
Um, that's because you need a list of paths, not just a path. How would the list comprehension know that you want to use a list of pngs in that directory?? Try using glob or os.listdir. – ShlomiF May 10 '20 at 18:29
@Phicalc, did this answer your question? If so it's customary to accept, so as to benefit the contributor as well as the community as a whole. – ShlomiF May 10 '20 at 20:40
@Phicalc , you just need to have a ``plt.savefig("image{i}.png".format(i=i))`` with a ``list_of_im_paths.append("/your_path_to_fig_folder/image{i}.png".format(i=i))`` inside your loop (that creates your figures). This way, you create a list with paths to each figure. (And also, I think you will need to define an empty list ``list_of_im_paths=[]`` just before your loop). – Diving May 21 '22 at 01:43

score 0 · Answer 2 · answered May 14 '20 at 00:39

The faster way is to use imageio as in @ShlomiF's answer, but you can do the same thing with pure matplotlib if you so prefer:

import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation

nframes = 25
plt.subplots_adjust(top=1, bottom=0, left=0, right=1)

def animate(i):
    im = plt.imread('image'+str(i)+'.png')
    plt.imshow(im)

anim = FuncAnimation(plt.gcf(), animate, frames=nframes, interval=(2000.0/nframes))
anim.save('output.gif', writer='imagemagick')

But if your first priority is the quality of the output you may want to consider using ffmpeg and convert directly,

ffmpeg -f image2 -i image%d.png output.mp4

ffmpeg -i output.mp4 -vf "fps=10,scale=320:-1:flags=lanczos" -c:v pam -f image2pipe - | \
          convert -delay 10 - -loop 0 -layers optimize output.gif

Changing the scale argument as needed to control the size of the final output, scale=-1:-1 leaves the size unchanged.

Creating an animation out of Matplotlib .pngs

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