from PIL import Image

im = Image.open("BarredRock.jpg")
width, height = im.size

def wash(c):
    n = c * 2
    if(n > 255):
        n = 255
    return n

pix = im.load()
print pix[500, 500]
for i in range(width):
    for j in range(height):
        pix[i, j] = tuple([wash(c) for c in pix[i,j]])

im.show()