A Python script to pixelate an image and add a thin black margin between the simulated pixels.

pixelate_image.py

from PIL import Image

backgroundColor = (0,)*3
pixelSize = 9

image = Image.open('input.png')
image = image.resize((image.size[0]/pixelSize, image.size[1]/pixelSize), Image.NEAREST)
image = image.resize((image.size[0]*pixelSize, image.size[1]*pixelSize), Image.NEAREST)
pixel = image.load()

for i in range(0,image.size[0],pixelSize):
  for j in range(0,image.size[1],pixelSize):
    for r in range(pixelSize):
      pixel[i+r,j] = backgroundColor
      pixel[i,j+r] = backgroundColor

image.save('output.png')

from PIL import Image
import os

Open Image

img = Image.open("example2.png")

imgSmall = img.resize((64, 64)) #smaller size will generate more pixelate results
result = imgSmall.resize(img.size,Image.NEAREST)

Save

result.save('result.png')

P.S: This doest what I exactly wanted.

@qaixerabbas
Haven't checked but I'm pretty sure that it's due to the differrence of division operators in python 2.7 and 3 . Replace all 4 occurrences of / with //, so that it would be integer division again, and it should be OK