imgdiff.py

import sys
import PIL
from PIL import ImageChops
from functools import reduce
import math, operator

def rmsdiff(im1, im2):
    "Calculate the root-mean-square difference between two images"

    h = ImageChops.difference(im1, im2).histogram()

    print h
    # calculate rms
    return math.sqrt(reduce(operator.add,
        map(lambda h, i: h*(i**2), h, range(256))
    ) / (float(im1.size[0]) * im1.size[1]))


if __name__ == '__main__':
    a= PIL.Image.open(sys.argv[1])
    b= PIL.Image.open(sys.argv[2])
    print (rmsdiff(a,b))