hideMessage_graphicstego3.py

from PIL import Image
import sys
import os

def hide(im, message):
    new_im = Image.new('RGB', im.size)
    idx = 0
    for x in range(im.width):
        for y in range(im.height):
            r, g, b = im.getpixel((x, y))
            if idx < len(message):
                b = ord(message[idx])
            new_im.putpixel((x, y), (r, g, b))
            idx += 1
    return new_im

def main():
    if len(sys.argv) != 4:
        print 'Usage: python %s <input-file> <message> <output-file>' % sys.argv[0]
        exit(1)

    input_file   = sys.argv[1]
    message      = sys.argv[2]
    output_file  = sys.argv[3]

    if not os.path.exists(input_file):
        print 'File "%s" does not exist' % input_file
        exit(1)

    im = Image.open(input_file)
    new_im = hide(im, message)
    new_im.save(output_file)


if __name__ == '__main__':
    main()