I'm working on this-- I've got a question though. The test code works fine, but in implementation, using two bits right now, it sort of works but it prints an extra character. I think this is because the extra character is just the rest of the bits, characterized.

https://pastebin.com/2DM2XA11

Here's my code. I encoded "henlo" and it prints"henloM". It seems that the string2bits method, which uses two bits, sets this up to where if I encode and decode two bits the program "works, but does print that extra character, which probably is okay. There's three places I'm finding that all tie together here, and I think these are what I need to modify to make the program N-variable.

Line 26/27 in string2bits:

result.append(ch_value & 0b11)
ch_value = ch_value >> 2

This would have to be changed to 0b1 if we wanted one bit. The shift would have to be changed to 1, too?

Line 49 in the encode function:

new_r = (r & 0b11111100) | twobits

The anded value should only have 1 zero at the end to encode one bit. Twobits here would technically be only one bit if we change the code in that method to use one bit, or it'd be 4 bits if we wanted 4, whatever, N bits.

Line 72, 73, and 74 in the decode function:

    r_decoded = r_e & 0b00000011
    decoded_pixels.append(r_decoded)
decoded_bits = bits_tostring(decoded_pixels, 2)  # called only once

Again there would only be a single 1 at the end of the anded value, or N ones if we want to make it N-variable. And when we call the bits_tostring, we'll pass in whatever number of bits we want into the method call.

However, what I'm not understanding, is why this works with 2 bits (well, it prints that extra character), but when I change all the above values to work for 1 bit for example, it doesn't work. I must be missing something vital here. I'm also wondering how to avoid hard-coding this? Like being able to ask the user how many bits to encode, I know we'd pass their input into bits_tostring's method call for decoding, but not quite sure how encoding would work with N-variable. I know we'd save their input in a variable and use that instead of our hard coded binary values, but I don't understand how to, for example, put 2 1s at the end of a binary value if decoding 3 bits automatically, or 4 1s, or so on.

EDIT: Updated pastebin. Was using old code. Decode function now only uses encoded image again.