import ImageChops
import math, operator

def equal(im1, im2):
    return ImageChops.difference(im1, im2).getbbox() is None

# Example: File: imagediff.py




def rmsdiff(im1, im2):
    "Calculate the root-mean-square difference between two images"
        
    h = ImageChops.difference(im1, im2).histogram()

    # 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]))

import Image
im = Image.open("bride.jpg")
im.rotate(45).show()