def center_on(image, location):
    h = image.size[0]
    w = image.size[1]

    return (int(location[0] - (0.5 * h)),int(location[1] - (0.5 * w)))

def scale(image, amount):
    return image.resize((int(image.size[0] * amount), int(image.size[1] * amount)))