Co-Occurrence Matrix

import numpy as np
file1 = open("contrast.txt","w")
arr = np.zeros((256, 256))
sum = 0
img = Image.open("Ocean_a.bmp")
gray_img = img.convert('L')
for i in range (0,gray_img.size[0]):
    for j in range (0,gray_img.size[1] - 1):
        currPixel = gray_img.getpixel((i, j))
        currPixel1 = gray_img.getpixel((i, j + 1))
        arr[currPixel,currPixel1] = arr[currPixel,currPixel1] + 1;
for i in range (0,arr.shape[0]):
    for j in range (0,arr.shape[1]):
        sum += arr[i,j]*np.power((i-j), 2)
file1.write("Ocean_a.bmp: "+str(sum))
file1.write("\n")
print(sum)
arr = np.zeros((256, 256))
sum = 0
img = Image.open("Ocean_b.bmp")
gray_img = img.convert('L')
for i in range (0,gray_img.size[0]):
    for j in range (0,gray_img.size[1] - 1):
        currPixel = gray_img.getpixel((i, j))
        currPixel1 = gray_img.getpixel((i, j + 1))
        arr[currPixel,currPixel1] = arr[currPixel,currPixel1] + 1;
for i in range (0,arr.shape[0]):
    for j in range (0,arr.shape[1]):
        sum += arr[i,j]*np.power((i-j), 2)
file1.write("Ocean_b.bmp: "+str(sum))
print(sum)
file1.close()