import media

filename = media.choose_file()
pic = media.load_picture(filename)
media.show(pic)

for pixel in pic:
    value = media.get_green(pixel)
    value = int(value*0.7)
    media.set_green(pixel, value)
    media.set_blue(pixel, int(0.7*media.get_blue(pixel)))

media.show(pic)