grayscale.py

from PIL import Image
import math

# creating a image object 
img = Image.open('selenagomez.png')
px = img.load()
height, width = img.size

new_image = Image.new(img.mode, img.size)

for row in range(0, height):
    for column in range(0, width):
        red, blue, green = px[row, column]
        avg = math.floor((red + blue + green)/3)
        new_image.putpixel((row, column), (avg, avg, avg))


new_image.show()