crypto300.py

import Image
import sys

def chunks(data, n):
    "Yield successive n-sized chunks from data"
    
    for i in xrange(0, len(data), n):
        yield data[i:i+n]

width = 2880
height = 5000 # some arbitrary height

img = Image.new('L', (width, height), 'white')
img_data = list(img.getdata())

bmp = open('crypted.bmp', 'rb').read()

white = bmp[0:16]
reverse_chunks = list(chunks(bmp, 16))[::-1]
for i, chunk in enumerate(reverse_chunks):
    for j in range(i * 6, (i +1) * 6):
        c = int(chunk == white) * 255
        img_data[j] = c

img.putdata(img_data)
img.save('result.png')