ffmpeg-gif.sh

#!/bin/sh

palette="/tmp/palette.png"

filters="fps=15,scale=$3:-1:flags=lanczos"

ffmpeg -v warning -i $1 -vf "$filters,palettegen" -y $palette
ffmpeg -v warning -i $1 -i $palette -lavfi "$filters [x]; [x][1:v] paletteuse" -y $2

gifff.py

#!/usr/bin/env python
from subprocess import call
import os
import sys

filename = sys.argv[1]
filename_target = filename + '.gif'
filesize_target = int(sys.argv[2] if len(sys.argv) > 2 else 5) * 1024 * 1024

min_resolution, max_resolution = (100, 1124)
while min_resolution < max_resolution:
  avg = (max_resolution + min_resolution) / 2
  call(('ffmpeg-gif.sh', filename, filename_target, str(avg)))
  size = os.stat(filename_target).st_size
  if size > filesize_target:
    max_resolution = avg - 1
  elif size < filesize_target:
    min_resolution = avg + 1
  else:
    min_resolution = max_resolution = (avg, avg)
call(('ffmpeg-gif.sh', filename, filename_target, str(min(min_resolution, max_resolution))))