donno2048 / stepng Goto Github PK

I wrote this steganographic algorithm to take an image and hide data in it:

output = [bin(i).replace('0b', '') for i in open('input.png', 'rb').read()]
bin_text = [bin(i).replace('0b', '').zfill(8) for i in bytearray(text + '\x00', 'utf8')]
for i in range(len(bin_text)):
    for j in range(8):
        output[index + 8 * i + j] = output[index + 8 * i + j][:-1] + bin_text[i][j]
open('output.png', 'wb').write(b''.join([int(i, 2).to_bytes(1, 'big') for i in output]))

Where text is the text hidden in the image, input.png is the input image and index is the starting index for the process,

The way it works is by hiding binary bits in the LSB's of the image.

The reading-back works perfectly but the writing creates very weird images.

For example, if I use this image:

To hide this message "Hi!" with starting index of 10000 I will get:

As you can see, the image is cropped after the chosen binary index, but why is that?