#! /usr/bin/python

import os
import sys
import md5
import cStringIO as StringIO

key = 'breadfruit chawbacon'
src = os.path.dirname(sys.argv[0])

class md5file:
    def __init__(self, fn='outf.bin'):
        self.fn = fn
        self.f = open(fn, 'wb')
        self.m = md5.new()

    def write(self, s):
        self.f.write(s)
        self.m.update(s)

    def close(self):
        self.f.close()
        os.rename(self.fn, self.m.hexdigest())

os.system('wget -O lena.tif http://www.cs.cmu.edu/~chuck/lennapg/lena_std.tif')
inf = os.popen('tifftopnm lena.tif', 'rb')
version = inf.readline()
dimensions = inf.readline()
depth = inf.readline()

# Read in plaintext
noise = open(os.path.join(src, 'noise.txt')).read()
noise += '\n\nThe key is "%s".\n' % key
noise = StringIO.StringIO(noise)

# Set the low-order bits in output file
outf = md5file()
outf.write(version)
outf.write(dimensions)
outf.write(depth)
i = 0
while True:
    c = noise.read(1)
    if c:
        c = ord(c)
    else:
        c = 0
    img_bytes = inf.read(8)
    if not img_bytes:
        break
    for j in range(8):
        bit = 7 - j
        img_byte = ord(img_bytes[j]) & 0xFE
        noise_bit = (c & (1<<bit)) >> bit
        out_byte = img_byte | noise_bit
        outf.write(chr(out_byte))
outf.close()

open('key', 'w').write(key)
os.unlink('lena.tif')