def _lsb_dct_coefficient_encode(image, output, message, nbits=1):
assert len(image.quantization) * 64 >= len(message) * 8
bit_mask = (1 << nbits) - 1
msg_iter = iter_bits(message, nbits)
for i in range(len(image.quantization)):
for j, msg_bit in zip(range(64), msg_iter):
image.quantization[i][j] = (image.quantization[i][j] & ~bit_mask) | msg_bit
image.save(output, qtables=image.quantization)
return image
def test_iter_bits_double(self):
# Try comparing chunks returned by iter_bits (when chunksize=2)
# to string returned by bin() using capital letters
# e.g. 'A' == 65 == 0b1000001
# iter_bits('A', chunksize=2) == [01, 00, 00, 01]
for o in range(65, 91):
char = chr(o)
bits = list(iter_bits(char, chunksize=2))
exp_bin_str = '{:08b}'.format(o)
bin_str = self._bin_str_from_chunks(bits, chunksize=2)
self.assertEqual(bin_str, exp_bin_str)
def test_iter_bits_single(self):
# Try comparing bits returned by iter_bits to string returned
# by bin() using capital letters from the alphabet.
for o in range(65, 91):
char = chr(o)
bits = list(iter_bits(char))
while bits[0] == 0 and len(bits) > 1:
# bin() drops leading zeros
bits.pop(0)
bin_str = '0b' + ''.join(map(str, bits))
self.assertEqual(bin_str, bin(o))
def _lsb_pixel_encode(image, output, message, nbits=1):
assert fits_in_image(image, message, nbits)
# TODO: can this be accomplished with Image.tobytes/frombytes/BytesIO or ImageChops with a dummy message Image
# Encode nbits of the message into each of the three color-components (RGB)
# for each pixel until we're at the end of the message.
# The bit mask needs to capture the least nbits significant bits.
pixels = image.load()
bit_mask = (1 << nbits) - 1
msg_iterator = grouper(iter_bits(message, chunksize=nbits), 3)
for xy, msg_part in zip(iter_coords(image), msg_iterator):
rgb = tuple((component & ~bit_mask | chunk) if chunk is not None else component
for component, chunk in zip(pixels[xy], msg_part))
pixels[xy] = rgb
image.save(output)
return image
