def decode(image):
""" takes an encoded image and returns the message that was
encoded inside that image.
Arguments:
image -- the image to be encoded. Image must be in the format
generated by the SimpleImage module (i.e. a list of lists
of tuples, where each tuple represents a pixel)
"""
output = ''
curr_chunk = ''
for row in image:
for pixel in row:
for num in pixel:
curr_chunk += bits.get_bit(num,0)
if len(curr_chunk) == BYTE_LENGTH:
if curr_chunk == ZERO_BYTE:
# found a byte 00000000, so no more message to
# decode
return output
else:
output += bits.bits_to_char(curr_chunk)
curr_chunk = ''
return output
def extractor(line,position):
bit_str = ''
for pixel in line:
for intensity in pixel:
bit_str += bits.get_bit(intensity,position)
line_str = bits.bits_to_message(bit_str)
line_n = int(line_str)
return line_n
def decode_ext(image, num_bits):
message_bit = ''
for row in image:
for a in range(len(image[0])):
for b in range(len(image[0][0])):
pixel_int = (row[a][b])
for count in range(num_bits):
message_bit += bits.get_bit(pixel_int, count)
message = bits_to_message(message_bit)
return message
def decode(image):
message_bit = ''
for row in image:
for a in range(len(image[0])):
for b in range(len(image[0][0])):
#The nested for loops help access the elements inside
#the tuples that are the intensity values.
pixel_int = (row[a][b])
#The intensity value is assigned to a variable.
message_bit += bits.get_bit(pixel_int, 0)
#The get_bit function in the bits.py module is called here
#to access the last bit of the intensity value represented
#in base 2. The last_bit would be '0' or '1'. The last bits
#of all the intensity values are concatenated and stored
#in a variable called message_bit.
message = bits_to_message(message_bit)
#The function bits_to_message is used to recover the original message.
return message
def decode(image):
"""
Takes an image as its argument and returns a string of ASCII characters
as its result.
Decoding process:
- Iterate over each intensity value in each pixel and do the following:
- Convert intensity value of image to binary
- Index LSB of intensity value and append it to a growing list
of bits
- After this operation, a string of bits is obtained, a part of which
(or all of it) is the bitstream of the coded message.
- Decode the entire string of bits using the bit_to_message function
Inputs:
image: a two-dimensional list of pixels, in zero-based row-major
order. Each pixel is a three element tuple of integers in the
range [0,255]
Result:
A string of ASCII characters, decoded from image using steganography
scheme described above.
Examples:
>>> decode(encode(test_image,''))
''
>>> decode(encode(test_image,'hi'))
'hi'
>>> decode(encode(test_image,'hello'))
'he'
"""
bitstream = ''
for row in image:
for pixel in row:
for intensity in pixel:
# Use get_bit function from bits.py library
# to select the LSB of each intensity value
bitstream += bits.get_bit(intensity,0)
# Decode message using bits_to_message function
message = bits.bits_to_message(bitstream)
return message
def decode_ext(image, num_bits):
"""
Very slight change from original decode function;
addition of extra nested 'for' loop allows iteration over
one intensity value to extract multiple code bits, as
determined by num_bits input
"""
if not(0 < num_bits <= 8):
print ('Number of bits must be an integer between 1 and 8\
inclusive')
return None
bitstream = ''
for row in image:
for pixel in row:
for intensity in pixel:
# Extra 'for' loop so more than one bit can be
# selected from each intensity value
for pos in range(num_bits):
bitstream += bits.get_bit(intensity,pos)
message = bits.bits_to_message(bitstream)
return message
from PIL import Image
import numpy as np
import sys, bits
src_img = Image.open(sys.argv[1])
pixels = np.array(src_img)
out_buffer = []
x = 0
y = 0
for i in range(int(sys.argv[2])):
buffer = 0
for j in range(8):
pixel = pixels[x][y]
bit = bits.get_bit(pixel[0], bits.LSB)
buffer = bits.set_bit(buffer, j, bit)
x += 1
if x >= src_img.width:
x = 0
y += 1
out_buffer.append(buffer)
fh = open(sys.argv[3], "wb")
fh.write(bytes(out_buffer))
import sys, bits
def array_image_save(array, image_path):
image = Image.fromarray(array)
image.save(image_path)
src_img = Image.open(sys.argv[1])
pixels = np.array(src_img)
fh = open(sys.argv[2], "rb")
binary_data = fh.read()
x = 0
y = 0
for i in range(len(binary_data)):
buffer = binary_data[i]
for j in range(8):
pixel = pixels[x][y]
bit = bits.get_bit(buffer, j)
pixel[0] = bits.set_bit(pixel[0], bits.LSB, bit)
pixels[x][y] = pixel
x += 1
if x >= src_img.width:
x = 0
y += 1
array_image_save(pixels, sys.argv[3])
print("Encoded %s bytes" % len(binary_data))
