Example of negative of an image with Python and Pygame

negative.py

import pygame

img = pygame.image.load('F:\input1.jpg')
W, H = img.get_width(), img.get_height()

for x in range(W):
   for y in range(H):
      color = pygame.Surface.get_at(img, (x,y))
      color = ~color
      pygame.Surface.set_at(img, (x,y), color)

pygame.image.save(img, 'F:\output.png')