monkey.py

from email.mime import base
import glob
import random
from PIL import Image

def random_base_img():
    img_fn = random.choice(glob.glob("./base_images/*.jpg"))
    return Image.open(img_fn, "r")


def modify_pixel(pixel, data):
    data_lst = [format(ord(d), '08b') for d in data]
    data_len = len(data_lst)
    imdata = iter(pixel)
 
    for i in range(data_len):
        pix = [value for value in imdata.__next__()[:3] +
                                imdata.__next__()[:3] +
                                imdata.__next__()[:3]]
 
        # Pixel value should be made
        # odd for 1 and even for 0
        for j in range(0, 8):
            if (data_lst[i][j] == '0' and pix[j]% 2 != 0):
                pix[j] -= 1
 
            elif (data_lst[i][j] == '1' and pix[j] % 2 == 0):
                if(pix[j] != 0):
                    pix[j] -= 1
                else:
                    pix[j] += 1
 
        # Eighth pixel of every set tells
        # whether to stop ot read further.
        # 0 means keep reading; 1 means thec
        # message is over.
        if (i == data_len - 1):
            if (pix[-1] % 2 == 0):
                if(pix[-1] != 0):
                    pix[-1] -= 1
                else:
                    pix[-1] += 1
 
        else:
            if (pix[-1] % 2 != 0):
                pix[-1] -= 1
 
        pix = tuple(pix)
        yield pix[0:3]
        yield pix[3:6]
        yield pix[6:9]

def encode(data): 
    print("encoding: ", data)
    base_img = random_base_img()
    w = base_img.size[0]
    (x, y) = (0, 0)
 
    for pixel in modify_pixel(base_img.getdata(), data):
        base_img.putpixel((x, y), pixel)
        if (x == w - 1):
            x = 0
            y += 1
        else:
            x += 1

    print("decoded:", decode(base_img.copy()))
    return base_img.copy()
 

def decode(img):
    data = ''
    imgdata = iter(img.getdata())

    while (True):
        pixels = [value for value in imgdata.__next__()[:3] +
                                imgdata.__next__()[:3] +
                                imgdata.__next__()[:3]]

        # string of binary data
        binstr = ''

        for i in pixels[:8]:
            if (i % 2 == 0):
                binstr += '0'
            else:
                binstr += '1'

        data += chr(int(binstr, 2))
        if (pixels[-1] % 2 != 0):
            return data