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- import PIL.Image
- import itertools
-
- import sys
-
-
- def get_bitstream(message):
- for c in message:
- bin_string = "{:08b}".format(c)
- for bit in bin_string:
- yield int(bit)
-
-
- def parse_bitstream(stream):
- for bits in by_chunk(stream, 8, fillvalue=0):
- binstr = "".join([str(b) for b in bits])
- c = int(binstr, 2)
- if chr(c) == "\n":
- break
- yield c
-
-
- def by_chunk(iterable, size, fillvalue=0):
- "Collect data into fixed-length chunks or blocks"
- args = [iter(iterable)] * size
- return itertools.zip_longest(*args, fillvalue=fillvalue)
-
-
- def set_bit(old_byte, new_bit):
- b = list(bin(old_byte))
- b[-1] = str(new_bit)
- return int("".join(b), 2)
-
-
- def main_encrypt():
- base_name = sys.argv[2]
- message = (sys.argv[3] + "\n").encode()
- carrier_name = base_name.replace(".png", ".carrier.png")
- base_image = PIL.Image.open(base_name)
- width, height = base_image.size
- new_image = PIL.Image.new("RGB", (width, height), "white")
- bitstream = get_bitstream(message)
- for row in range(height):
- for col in range(width):
- r, g, b = base_image.getpixel((col, row))
- value = None
- try:
- value = next(bitstream)
- except StopIteration:
- pass
- if value is not None:
- r = set_bit(r, value)
- new_image.putpixel((col, row), (r, g, b))
-
- new_image.save(carrier_name, "png")
- print("carrier written to", carrier_name)
-
-
- def yield_bits(carrier_image):
- width, height = carrier_image.size
- for row in range(height):
- for col in range(width):
- r, g, b = carrier_image.getpixel((col, row))
- last_bit = int(bin(r)[-1])
- yield last_bit
-
-
- def main_decrypt():
- carrier_name = sys.argv[2]
- carrier_image = PIL.Image.open(carrier_name)
- encoded = yield_bits(carrier_image)
- decoded = bytes(parse_bitstream(encoded))
- print(decoded.decode())
-
-
- def main():
- if sys.argv[1] == "encrypt":
- main_encrypt()
- elif sys.argv[1] == "decrypt":
- main_decrypt()
- else:
- sys.exit("choose from encrypt, decrypt")
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