Python: PIL ( Pillow ) NumPy add images

PillowNumpyAddImages.py

from itertools import izip

from PIL import Image
import numpy as np

def getImageDifference(x, y):
    diff3 = 1.0
    # http://rosettacode.org/wiki/Percentage_difference_between_images#Python
    if x.size == y.size:
        pairs = izip(x.getdata(), y.getdata())
        if len(x.getbands()) == 1:
            # for gray-scale jpegs
            diff3 = sum(abs(p1 - p2) for p1, p2 in pairs)
        else:
            diff3 = sum(abs(c1 - c2) for p1, p2 in pairs for c1, c2 in zip(p1, p2))
        ncomponents = x.size[0] * x.size[1] * 3
        diff3 = (diff3 / 255.0 * 100) / ncomponents
    return diff3

i1 = Image.open('1.png').convert(mode='L', dither=Image.NONE)
i2 = Image.open('2.png').convert(mode='L', dither=Image.NONE)
cc = Image.open('C.png').convert(mode='L', dither=Image.NONE)

# Variation 1

pixelThreshold = 200
i1 = np.array(i1)
i1 = np.where(i1 > pixelThreshold, 255, 0)
i2 = np.array(i2)
i2 = np.where(i2 > pixelThreshold, 255, 0)
final1 = (i1+i2)/2
final1 = np.where(final1 > pixelThreshold, 255, 0)
final1 = Image.fromarray(final1.astype(np.uint8))
final1.show()

print getImageDifference(final1, cc) # ==> 0.12561853664

# # Variation 2
# pixelThreshold = 200
# i1 = np.array(i1)
# i1 = np.where(i1 > pixelThreshold, 255, 0)
# i2 = np.array(i2)
# i2 = np.where(i2 > pixelThreshold, 255, 0)
# final1 = np.minimum((i1+i2),256)
# final1 = Image.fromarray(final1)
# final1.show()
#
# # Variation 3
# pixelThreshold = 200
# i1 = np.array(i1)
# i1 = np.where(i1 > pixelThreshold, 255, 0)
# i2 = np.array(i2)
# i2 = np.where(i2 > pixelThreshold, 255, 0)
# final1 = (i1+i2)/2
# final1[final1>256]=256
# final1 = Image.fromarray(final1)
# final1.show()
#
# # Variation 4
i1 = Image.open('1.png').convert(mode='L', dither=Image.NONE)
i2 = Image.open('2.png').convert(mode='L', dither=Image.NONE)

# final2 = Image.blend(i1, i2, 0.5)
# print getImageDifference(final2, cc) # ==> 0.661266633307

# # Variation 5
final2 = Image.composite(i1, i2, i2)
final2.show()

print getImageDifference(final2, cc) # ==> 0.0380851773602

# courtsey : https://stackoverflow.com/questions/524930/numpy-pil-adding-an-image/