Extract frames from an animated GIF, correctly handling palettes and frame update modes

gifextract.py

import os
from PIL import Image


'''
I searched high and low for solutions to the "extract animated GIF frames in Python"
problem, and after much trial and error came up with the following solution based
on several partial examples around the web (mostly Stack Overflow).

There are two pitfalls that aren't often mentioned when dealing with animated GIFs -
firstly that some files feature per-frame local palettes while some have one global
palette for all frames, and secondly that some GIFs replace the entire image with
each new frame ('full' mode in the code below), and some only update a specific
region ('partial').

This code deals with both those cases by examining the palette and redraw
instructions of each frame. In the latter case this requires a preliminary (usually
partial) iteration of the frames before processing, since the redraw mode needs to
be consistently applied across all frames. I found a couple of examples of
partial-mode GIFs containing the occasional full-frame redraw, which would result
in bad renders of those frames if the mode assessment was only done on a
single-frame basis.

Nov 2012
'''


def analyseImage(path):
    '''
    Pre-process pass over the image to determine the mode (full or additive).
    Necessary as assessing single frames isn't reliable. Need to know the mode 
    before processing all frames.
    '''
    im = Image.open(path)
    results = {
        'size': im.size,
        'mode': 'full',
    }
    try:
        while True:
            if im.tile:
                tile = im.tile[0]
                update_region = tile[1]
                update_region_dimensions = update_region[2:]
                if update_region_dimensions != im.size:
                    results['mode'] = 'partial'
                    break
            im.seek(im.tell() + 1)
    except EOFError:
        pass
    return results


def processImage(path):
    '''
    Iterate the GIF, extracting each frame.
    '''
    mode = analyseImage(path)['mode']
    
    im = Image.open(path)

    i = 0
    p = im.getpalette()
    last_frame = im.convert('RGBA')
    
    try:
        while True:
            print "saving %s (%s) frame %d, %s %s" % (path, mode, i, im.size, im.tile)
            
            '''
            If the GIF uses local colour tables, each frame will have its own palette.
            If not, we need to apply the global palette to the new frame.
            '''
            if not im.getpalette():
                im.putpalette(p)
            
            new_frame = Image.new('RGBA', im.size)
            
            '''
            Is this file a "partial"-mode GIF where frames update a region of a different size to the entire image?
            If so, we need to construct the new frame by pasting it on top of the preceding frames.
            '''
            if mode == 'partial':
                new_frame.paste(last_frame)
            
            new_frame.paste(im, (0,0), im.convert('RGBA'))
            new_frame.save('%s-%d.png' % (''.join(os.path.basename(path).split('.')[:-1]), i), 'PNG')

            i += 1
            last_frame = new_frame
            im.seek(im.tell() + 1)
    except EOFError:
        pass


def main():
    processImage('foo.gif')
    processImage('bar.gif')
    

if __name__ == "__main__":
    main()

Thanks @JankesJanco – it's been many years since I went anywhere near this, but I'm glad it's been useful for some folks! I agree that using a library like moviepy is probably going to be more reliable these days.

Hi Biggles,
you did a great job! There are many, many ... many coders searching for this solution.
Best regards
Axel Arnold Bangert - Herzogenrath 05.03.2020

How would you save the changed frames inside the gif as a new animated gif? With this we could operate on frames inside the gif and save it.
Axel

Hi Axel, that's a little outside of the scope of this code I'm afraid – I also haven't touched it in many years so there are probably better solutions out there by now. moviepy is mentioned above, that might help. In any case I hope it was helpful.

Hi James, I am a beginner with python. I tried some things with the old Fireworks Console of John Dunning. But there are some bugs in it ( feather select and so on). This combination of Python and FW *.jsx works But it is silly. So I try to do some things only with Python and try to optimize that. Yes you are right, there are newer packages, which work with animated gifs (imageio e.g.), but I did not find out how to get the pixel-data with coordinates out from there. I'll see. Thanks for your answer and have a nice day - here (Aachen-Germany) they are all mad about Corona-Virus :) Best regards Axel Von: James Tiplady [mailto:[email protected]] Gesendet: Donnerstag, 5. März 2020 17:37 An: BigglesZX Cc: Axel Arnold Bangert; Comment Betreff: Re: BigglesZX/gifextract.py Hi Axel, that's a little outside of the scope of this code I'm afraid – I also haven't touched it in many years so there are probably better solutions out there by now. moviepy is mentioned above, that might help. In any case I hope it was helpful. You are receiving this because you commented. Reply to this email directly

Hi Axel – that's great, always nice to hear from other people. Buying extra pasta in London today :). Good luck with your project and stay healthy! James

Hi James, your extra pasta has been fine :) ? OK :) ... guess that this works. I found it at https://stackoverflow.com/questions/50054187/convert-animated-gif-to-4d-array-in-python import numpy as np from PIL import Image, ImageSequence img = Image.open('test.gif') frames = np.array([np.array(frame.copy().convert('RGB').getdata(),dtype=np.uint8).reshape(frame.size[1],frame.size[0],3) for frame in ImageSequence.Iterator(img)]) Best Axel Von: James Tiplady [mailto:[email protected]] Gesendet: Freitag, 6. März 2020 12:46 An: BigglesZX Cc: Axel Arnold Bangert; Comment Betreff: Re: BigglesZX/gifextract.py Hi Axel – that's great, always nice to hear from other people. Buying extra pasta in London today :). Good luck with your project and stay healthy! James — You are receiving this because you commented.

Due to PIL updates, to continue using this file as is this would be a possible solution

        if not im.getpalette() and im.mode in ("L", "LA", "P", "PA"):  
            im.putpalette(p)