Optimize a gif to a specific file size

perfectgif.py

#!/usr/bin/env python3

import sys
import os
import ffmpeg
from pygifsicle import optimize


frames_path = sys.argv[1]
output_name = sys.argv[2]

palette_filename = 'palette.png'


def generate_gif(colors, suffix, **kwargs):

    print('.', end='', flush=True)

    output_filename = '{}_{}.gif'.format(output_name, suffix)

    # Generate palette
    (
        ffmpeg
        .input('{}/*.png'.format(frames_path), pattern_type='glob')
        .filter('palettegen', stats_mode='diff', max_colors=colors, reserve_transparent=False)
        .output(palette_filename)
        .overwrite_output()
        .run(quiet=True)
    )

    # Generate gif
    palette = (
        ffmpeg
        .input(palette_filename)
    )
    frames = (
        ffmpeg
        .input('{}/*.png'.format(frames_path), pattern_type='glob')
    )
    (
        ffmpeg
        .filter((frames, palette), 'paletteuse', **kwargs)
        .output(output_filename)
        .overwrite_output()
        .run(quiet=True)
    )
    optimize(output_filename, options=['--optimize=03', '--delay=6', '--no-warnings'])

    size = os.stat(output_filename).st_size
    return size


def binary_search(func, low, high, target):

    while low <= high:

        mid = low + (high - low) // 2
        candidate = func(mid)

        # Check if x is present at mid 
        if candidate == target:
            return (candidate, mid)
  
        # If candidate is greater, ignore left half
        elif candidate < target:
            low = mid + 1

        # If candidate is smaller, ignore right half 
        else:
            high = mid - 1
  
    if candidate > target:
        candidate = func(mid - 1)

    return (candidate, mid)


def configure_generate_gif(**kwargs):
    suffix = '-'.join(str(v) for v in kwargs.values())
    def func(colors):
        return generate_gif(colors, suffix, **kwargs)
    return (suffix, func)

configurations = [
    configure_generate_gif(dither='bayer', bayer_scale=1),
    configure_generate_gif(dither='bayer', bayer_scale=2),
    configure_generate_gif(dither='bayer', bayer_scale=3),
    configure_generate_gif(dither='floyd_steinberg'),
    configure_generate_gif(dither='sierra2'),
    configure_generate_gif(dither='sierra2_4a'),
]

for suffix, func in configurations:
    print(suffix, end='', flush=True)
    final_size, final_colors = binary_search(func, 1, 256, 2000000)
    print(' {} bytes, {} colours'.format(final_size, final_colors))