Given a directory, compress all images in it

compress_images.py

import sys, os
from PIL import Image

files = os.listdir(sys.argv[1])

for i, f in enumerate(files):
    fname = os.path.join(sys.argv[1], f)
    im = Image.open(fname).save(fname)
    print 'Compressing {} of {}'.format(i, len(files))