ffmepg2gif.py

#! /usr/bin/python3

# create a gif from a video using ffmpeg and imagemagick.
# both ffmpeg and imagemagick must be installed and added to the PATH env variable for this to work.
# if I were being fancier, I'd make this take command line arguments instead of just setting
# variables inside the `if __name__ == '__main__'` block, but it's intended for personal use only
# so whatever.

import os
import subprocess
import shutil
import re


def get_pngs(folder=None):
    # return a list of .png files in a folder, sorted by filename.
    if not folder:
        folder = os.getcwd()
    files = sorted([
        os.path.join(folder, f)
        for f in os.listdir(folder)
        if os.path.isfile(os.path.join(folder, f))
        and os.path.splitext(f)[1].lower() == '.png'
    ])
    return files

def export_img_seq(filepath, tempdir, start, end):
    # export an image sequence from a video using ffmpeg. `start` and `end` must be time strings
    # as supported by ffmpeg, eg. '01:20:30' for 1h 20m and 30s into the video
    ffmargs = [
        'ffmpeg',
        '-i', filepath,
        '-ss', start,
        '-to', end,
        '-f', 'image2',
        os.path.join(tempdir, '%04d.png')
    ]
    print(' '.join(ffmargs))
    p = subprocess.Popen(ffmargs)
    p.wait()


def gif(seq_dir, outfile, delay=4, resize='100%x100%'):
    # convert an image sequence into a gif using imagemagick.
    # image sequence is assumed to be ordered pngs from export_img_seq(); other image sets might do
    # weird things.
    # seq_dir and outfile should be self-explanatory. Delay is in 1/100ths of a second, 
    # so delay=4 = 40ms/frame = 25fps.
    # resize can be in pixelsxpixels or percent%xpercent% format
    gif_args = [
        'convert',
        '-delay',  str(delay),
        '-loop',   '0',  # loop infinitely
        '-resize', resize,
        # ordered-dither setting here is kind of magic; it tries to guess a good colour map to use.
        # It seems to work pretty well; I don't recommend messing with it too much.
        '-ordered-dither', 'o8x8,23', '+map',
        os.path.join(seq_dir, '*.png'),
        outfile
    ]
    print(' '.join(gif_args))
    p = subprocess.Popen(gif_args)
    p.wait()


def text_over(
        seq_dir,
        start_frame,
        end_frame,
        text,
        gravity,
        font='Helvetica-Bold',
        pointsize='200',
        offset='0,0'
    ):
    # overlay text on a set of images inside seq_dir. Again, this sequence is assumed to have come
    # from export_img_seq() so I make no guarantees if your sequence did not.
    # 'gravity' is imagemagick's setting for text alignment. See their documentation for valid vals.
    imgmgk_args = [
        'convert',
        '',   # placeholder for input file
        '-fill', 'white',
        '-font', font,
        '-gravity', gravity,
        '-pointsize', str(pointsize),
        '-draw', "text {} '{}' ".format(offset, text),
        ''   # placeholder for output file
    ]
    images = get_pngs(seq_dir)
    for i in images[start_frame:end_frame]:
        i_args = imgmgk_args[:]
        i_args[1] = i   # set input file
        i_args[-1] = i  # set output file
        print(' '.join(i_args))
        p = subprocess.Popen(i_args)  # run the command
        p.wait()  # wait for imagemagick to finish


def find_timeframe(srt_file, phrase, index=0):
    # returns a (start, end) tuple of ffmpeg-compatible times based on the index'th instance of 
    # a phrase in the srt_file.
    srtTime = r'(\d{2}:\d{2}:\d{2}),\d{3}'
    reSearch = re.compile(
        r'\d\S*\n{} --> {}\S*\n.*{}'.format(srtTime, srtTime, phrase),
        re.MULTILINE + re.IGNORECASE
    )
    matches = reSearch.findall(open(srt_file).read())
    if len(matches) == 0:
        print('No lines found in subtitle file for {}'.format(phrase))
    elif len(matches) == 1:
        print('Found one match for "{}" in subtitle file'.format(phrase))
        return matches[0]
    else:
        print('Found {} matches for "{}" in subtitle file:'.format(len(matches), phrase))
        for m in matches:
            print(m)
        print('using match number {}'.format(index+1))
        return matches[index]
    quit()  # quit if we didn't return a valid match


if __name__ == '__main__':
    # input file
    filepath = '/data/media/videos/movies/James.Bond.GoldenEye.1995.mp4'
    filename = os.path.split(filepath)[-1]

    # output directories
    tempdir = '/data/pictures/temp'
    outdir = '/data/pictures/other/homemade_gifs'
    prepend = '01'  # use this value to set unique names for multiple gifs from the same source file
    outfile = os.path.join(outdir, os.path.splitext(filename)[0] + prepend + '.gif')
    if not os.path.exists(outdir):
        os.path.makedirs(outdir)
    tempdir = os.path.join(tempdir, filename, prepend)
    if not os.path.exists(tempdir):
        os.makedirs(tempdir)
    
    # start and end timestamps to extract. This will be compiled into a regex, so you can enter
    # a regular expressions to search. Normal text searches should also work fine, since subtitles
    # shouldn't contain anything that would get interpreted oddly as a regex.
    # You could also manually set start and end as ffmpeg-compatible timestamps (eg. 00:03:05)
    start, end = find_timeframe(
        '/data/media/videos/movies/James.Bond.GoldenEye.1995.srt',
        'Yes! I am invincible.',
        index=0
    )

    # now make an image sequence from the video
    export_img_seq(filepath, tempdir, start, end)

    # add text to images in the sequence. The first frame of the gif will be 0.
    # I usually set this up after making a textless gif first. Maybe in the future I'll try making
    # this occur automatically based off the subtitles.
    text_over(tempdir, 0, 21, 'YES!', 'West', pointsize='300', offset='80,0')
    text_over(tempdir, 21, 30, 'I', 'South', pointsize='225', offset='0,80')
    text_over(tempdir, 30, 36, 'AM', 'South', pointsize='225', offset='0,80')
    text_over(tempdir, 36, 64, 'INVINCIBLE!', 'South', pointsize='225', offset='0,80')

    # now smoosh the sequence back together into a gif
    gif(tempdir, outfile, resize='50%x50%', delay=4)
    print('successfully created {}'.format(outfile))

    # cleanup, if required
    shutil.rmtree(tempdir)

    # and now you've got the final gif - for example:
    # http://gfycat.com/UnlawfulImpishBluebottle