pixelate.py

#!/usr/local/bin/python3
from PIL import Image

# Open Paddington
img = Image.open("input_file_name.jpg")


#increase for high resulation
si=16

# Resize smoothly down to 16x16 pixels
imgSmall = img.resize((si,si),resample=Image.BILINEAR)

# Scale back up using NEAREST to original size
result = imgSmall.resize(img.size,Image.NEAREST)

# Save
result.save('output_file_name.jpg')