comparing images using PSNR

image_comparison.py

from PIL import Image
import math


def main():
    im1 = Image.open('dwarf.png')
    im2 = Image.open('dwarf2.png')
    width, height = im1.size
    print('{} {}'.format(width, height))
    pixels1 = im1.load()
    pixels2 = im2.load()
    mse = 0
    for y in range(0, height):
        for x in range(0, width):
            r1, g1, b1, _ = pixels1[x, y]
            r2, g2, b2, _ = pixels2[x, y]
            mse += (r1-r2) ** 2 + (g1-g2) ** 2 + (b1-b2) ** 2
    
    mse = mse / (width*height*3)
    psnr = 999999
    if mse > 0:
        psnr = 10 * math.log10( (255 ** 2) / mse)
    
    print('MSE = {}'.format(mse))
    print('PSNR = {}'.format(psnr))
    print('Image width={} height={}\n'.format(width, height))

if __name__ == '__main__':
    main()