steganography.py

import argparse

from PIL import Image


class Steganography:

    BLACK_PIXEL = (0, 0, 0)

    def _int_to_bin(self, rgb):
        """Convert an integer tuple to a binary (string) tuple.

        :param rgb: An integer tuple like (220, 110, 96)
        :return: A string tuple like ("00101010", "11101011", "00010110")
        """
        r, g, b = rgb
        return f'{r:08b}', f'{g:08b}', f'{b:08b}'

    def _bin_to_int(self, rgb):
        """Convert a binary (string) tuple to an integer tuple.

        :param rgb: A string tuple like ("00101010", "11101011", "00010110")
        :return: Return an int tuple like (220, 110, 96)
        """
        r, g, b = rgb
        return int(r, 2), int(g, 2), int(b, 2)

    def _merge_rgb(self, rgb1, rgb2, digit):
        """Merge two RGB tuples.

        :param rgb1: An integer tuple like (220, 110, 96)
        :param rgb2: An integer tuple like (240, 95, 105)
        :return: An integer tuple with the two RGB values merged.
        """
        r1, g1, b1 = self._int_to_bin(rgb1)
        r2, g2, b2 = self._int_to_bin(rgb2)
        rgb = r1[:digit] + r2[:8-digit], g1[:digit] + g2[:8-digit], b1[:digit] + b2[:8-digit]
        return self._bin_to_int(rgb)

    def _unmerge_rgb(self, rgb, digit):
        """Unmerge RGB.

        :param rgb: An integer tuple like (220, 110, 96)
        :return: An integer tuple with the two RGB values merged.
        """
        r, g, b = self._int_to_bin(rgb)
        # Extract the last 4 bits (corresponding to the hidden image)
        # Concatenate 4 zero bits because we are working with 8 bit
        new_rgb = r[digit:] + '0'*digit, g[digit:] + '0'*digit, b[digit:] + '0'*digit
        return self._bin_to_int(new_rgb)

    def merge(self, image1, image2, digit=4):
        """Merge image2 into image1.

        :param image1: First image
        :param image2: Second image
        :return: A new merged image.
        """
        # Check the images dimensions
        if image2.size[0] > image1.size[0] or image2.size[1] > image1.size[1]:
            raise ValueError('Image 2 should be smaller than Image 1!')

        # Get the pixel map of the two images
        map1 = image1.load()
        map2 = image2.load()

        new_image = Image.new(image1.mode, image1.size)
        new_map = new_image.load()

        for i in range(image1.size[0]):
            for j in range(image1.size[1]):
                is_valid = lambda: i < image2.size[0] and j < image2.size[1]
                rgb1 = map1[i ,j]
                rgb2 = map2[i, j] if is_valid() else self.BLACK_PIXEL
                new_map[i, j] = self._merge_rgb(rgb1, rgb2, digit)

        return new_image

    def unmerge(self, image, digit=4, binarization=True):
        """Unmerge an image.

        :param image: The input image.
        :return: The unmerged/extracted image.
        """
        pixel_map = image.load()

        # Create the new image and load the pixel map
        new_image = Image.new(image.mode, image.size)
        new_map = new_image.load()

        for i in range(image.size[0]):
            for j in range(image.size[1]):
                r, g, b = self._unmerge_rgb(pixel_map[i, j], digit)
                r = 255 if r >= 128 else 0
                g = 255 if g >= 128 else 0
                b = 255 if b >= 128 else 0
                new_map[i, j] = r, g, b 

        return new_image


def main():
    parser = argparse.ArgumentParser(description='Steganography')
    subparser = parser.add_subparsers(dest='command')

    merge = subparser.add_parser('merge')
    merge.add_argument('--image1', required=True, help='Image1 path')
    merge.add_argument('--image2', required=True, help='Image2 path')
    merge.add_argument('--output', required=True, help='Output path')

    unmerge = subparser.add_parser('unmerge')
    unmerge.add_argument('--image', required=True, help='Image path')
    unmerge.add_argument('--output', required=True, help='Output path')

    args = parser.parse_args()

    if args.command == 'merge':
        image1 = Image.open(args.image1)
        image2 = Image.open(args.image2)
        Steganography().merge(image1, image2).save(args.output)
    elif args.command == 'unmerge':
        image = Image.open(args.image)
        Steganography().unmerge(image).save(args.output)


if __name__ == '__main__':
    main()