full-color GIF simple

#!/usr/bin/env python2

import sys
import os.path
from PIL import Image
from collections import Counter

# Get the input file path:
_,path = sys.argv
root, _ = os.path.splitext(path)

# Open input image:
img = Image.open(path)
dat = img.getdata()
w,h = img.size
col = [ rgb for (rgb, cnt) in Counter(dat).most_common() ]
rev = dict((rgb,i) for (i, rgb) in enumerate(col))
idx = [ rev[rgb] for rgb in dat ]

# Generate a list of output images:
out = Image.new('P', img.size)
nfr = (len(col) + 253)//255
opt = {}
for frame in range(nfr):
    start = 255*frame + 1
    end   = min(start + 255, len(col))
    out.putpalette(sum(col[start - 1:end], tuple()))
    out.putdata([ 1 + i - start if start <= i < end else 0 for i in idx ])
    out.save('%s-%04d.gif' % (root, frame), **opt)
    opt['transparency'] = 0  # all frames except the first use transparency

# Since PIL doesn't support creating multi-frame GIF files, the resulting
# files must be converted with another tool.  I used gifsicle.