Example of adjusting contrast of an image with Python and Pygame

adjusting_contrast.py

import pygame

img = pygame.image.load('F:\input.jpg')
W, H = img.get_width(), img.get_height()
contrast = int(input())
F = (259 * (contrast + 255)) / (255 * (259 - contrast))

def fix_color(color):
    if color > 255:
        return 255
    elif color < 0:
        return 0
    else:
        return int(color)

for x in range(W):
    for y in range(H):
        color = pygame.Surface.get_at(img, (x,y))
        R , G , B = F * (color.r - 128) + 128, F * (color.g - 128) + 128, F * (color.b - 128) + 128
        R , G , B = fix_color(R), fix_color(G), fix_color(B)
        color.update(R,G,B)
        pygame.Surface.set_at(img, (x,y), color)

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