def decode(infile):
"""
Decode the data from a given file or file-like object.
:param infile: File path or file-like object.
:return: The encoded data as a byte array.
"""
encoded_image = Image.open(infile)
# If this is a multi-channel image, the call to getdata() will return
# an array of tuples for the pixel data. If this is a single-channel
# image, we just get an array of pixel values. To normalize this, we
# will try to flatten the array first. If this throws a TypeError, we
# can just assume we have a single-channel image.
try:
encoded_data = encoded_image.getdata()
encoded_data = itertools.chain.from_iterable(encoded_data)
encoded_data = bytearray(encoded_data)
except TypeError:
encoded_data = encoded_image.getdata()
encoded_data = bytearray(encoded_data)
decoded_byte = 0
decoded_bytes = bytearray()
current_byte = 0
# Find the size of the encoded data from the first N bytes of the image
size_bytes = struct.calcsize('l') * 8
for i in xrange(size_bytes):
if bits.is_bit_set(encoded_data[current_byte], 0):
decoded_byte = bits.set_bit(decoded_byte, 7 - (i % 8))
else:
decoded_byte = bits.unset_bit(decoded_byte, 7 - (i % 8))
if 7 - (i % 8) == 0:
decoded_bytes.append(decoded_byte)
current_byte += 1
decoded_size, = struct.unpack('l', str(decoded_bytes))
decoded_size *= 8
decoded_bytes = bytearray()
decoded_byte = 0
# Decode the original datas
for i in xrange(decoded_size):
if bits.is_bit_set(encoded_data[current_byte], 0):
decoded_byte = bits.set_bit(decoded_byte, 7 - (i % 8))
else:
decoded_byte = bits.unset_bit(decoded_byte, 7 - (i % 8))
if 7 - (i % 8) == 0:
decoded_bytes.append(decoded_byte)
current_byte += 1
return decoded_bytes
def encode(data, infile, outfile):
"""
Encode the given data in a new copy of a given image file.
:param data: Data to be encoded. This is typically a bytearray.
:param infile: The original image to use. This can be either a
file name or an open file object.
:param outfile: The new image to create. This can be either a
file name of an open file object.
"""
base_image = Image.open(infile)
# If this is a multi-channel image, the call to getdata() will return
# an array of tuples for the pixel data. If this is a single-channel
# image, we just get an array of pixel values. To normalize this, we
# will try to flatten the array first. If this throws a TypeError, we
# can just assume we have a single-channel image.
try:
composite_data = base_image.getdata()
composite_data = itertools.chain.from_iterable(composite_data)
composite_data = bytearray(composite_data)
except TypeError:
composite_data = base_image.getdata()
composite_data = bytearray(composite_data)
# Build a simple header that will hold the size of the encoded data.
# We use a structure here to make sure the header size itself remains
# consistent.
encoding_header = struct.pack('l', len(data))
# Prepend the header to the original data
full_data = bytearray(encoding_header)
full_data.extend(bytearray(data))
current_byte = 0
# Iterate over each byte in the input data.
for data_byte in full_data:
# Iterate over each bit in the input data byte in high-to-low order.
for bit_shift in xrange(7, -1, -1):
# If the current input bit is set, set the low bit in the current byte
# of the base image. Similarly, if the bit is unset, then unset the low
# bit of the current image byte.
if bits.is_bit_set(data_byte, bit_shift):
composite_data[current_byte] = bits.set_bit(composite_data[current_byte], 0)
else:
composite_data[current_byte] = bits.unset_bit(composite_data[current_byte], 0)
# Go on to the next byte in the base image
current_byte += 1
# Re-encode the data into a new image
data_image_size = base_image.size
composite_image = Image.frombytes(base_image.mode, data_image_size, str(composite_data))
# Save the image to the supplied output file
composite_image.save(outfile, format=base_image.format)
