Python.ImageEncoder/Python.ImageEncoder.py at master · FHArchive/Python.ImageEncoder · GitHub

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# Image encoder
""" Because I can't get my head around jpg compression and it often leads to
them behaving oddly, this program seems better suited to uncompressed images.
Admittedly this is far less useful in the wild but will still allow me to
practice some steganography. It will be best to use bmp images here"""

import os


# Define application constants
HEADER_SIZE = 1024
FOOTER_SIZE = 1024
MAX_SECRET_LEN = 1024
""" I've done an MD5 hash of "CLEAN" and appended it to the filename to reduce
the chance of overwriting an important file """
CLEAN_IMG_NAME = "CLEANa88a6a0c276fd853999a1faedf19c00e.bmp"


# Read image file in
def readImg(imageName):
	image = open(imageName, "rb")
	return image

# Write image file out
def writeImg(imageName):
	image = open(imageName, "wb")
	return image

# Get the size of the image in bytes to prevent overwriting footer
def getSize(imageName):
	return os.path.getsize(imageName)

# Replace the least significant bit with a 0
def writeCleanImg(inputImgName, outputImgName):
	# Take the input image and get its size
	inputImg = readImg(inputImgName)
	inputImgSize = getSize(inputImgName)

	# Create/ overwrite the output image
	outputImg = writeImg(outputImgName)

	# Copy the header
	outputImg.write(inputImg.read(HEADER_SIZE))

	# For the bytes not in the Header or Footer
	for _byte in range(inputImgSize - (HEADER_SIZE + FOOTER_SIZE)):

		# Set the LSB to 0 and write it to the output image
		partAsInt = (inputImg.read(1)[0] & 254)
		partAsByte = ((partAsInt).to_bytes(1, byteorder='big'))
		outputImg.write(partAsByte)

	# Copy the footer across
	outputImg.write(inputImg.read(FOOTER_SIZE))
	return 0

# Write a secret message to the image
def writeEncodedImg(inputImgName, outputImgName, secretMsg):
	# Take the input image and get its size
	inputImg = readImg(inputImgName)
	inputImgSize = getSize(inputImgName)

	# Create/ overwrite the output image
	outputImg = writeImg(outputImgName)

	# Copy the header across
	outputImg.write(inputImg.read(HEADER_SIZE))

	# For the bytes not in the Header or Footer
	for byte in range(inputImgSize - (HEADER_SIZE + FOOTER_SIZE)):

		# Set the LSB to a part of the text and write it to the output image
		partAsInt = (inputImg.read(1)[0] | calculateLSB(byte, secretMsg))
		partAsByte = ((partAsInt).to_bytes(1, byteorder='big'))
		outputImg.write(partAsByte)

	# Copy the footer across
	outputImg.write(inputImg.read(FOOTER_SIZE))
	return 0

def calculateLSB(byte, secretMsg):
	# Get the character to write
	try:
		charToWrite = secretMsg[byte // 8]
	except:
		# No character so nothing to write
		return 0
	# Select the correct bit
	bit = byte % 8
	# Get the bit to write
	charBit = (ord(charToWrite) >> bit) & 1
	return charBit

def readEncodedImg(inputImgName):
	# Take the input image and get its size
	inputImg = readImg(inputImgName)
	inputImg.read(HEADER_SIZE)
	# For the bytes not in the Header or Footer
	outString = ""
	for _byte in range(MAX_SECRET_LEN):
		charInt = 0
		for bit in range(8):
			# Read the LSB
			lsb = inputImg.read(1)[0] & 1
			charInt += lsb << bit
		outString += chr(charInt)

	print(outString)
	return 0

def cli():
	print("Clean, Encode, Clean and Encode (.bmp only), Decode or Quit? " +
		  "(C, e, a, d, q)")
	choice = input(">")[0].lower()

	# Quit application
	if choice == "q":
		return True

	# All functions require the path to the input image
	print("Type the name of the input image (include the file extension " +
		  "and path if required)")
	inputImgName = input(">")

	# Some functions require additional parameters
	if choice != "d":
		print("Type the name of the output image (include the file extension "+
			  "and path if required)")
		outputImgName = input(">")
	if choice in ["e", "a"]:
		print("Type the secret message (max " + str(MAX_SECRET_LEN) +
			  " characters)")
		secretMsg = input(">")

	# Run the required function for each choice
	# ENCODE
	if choice == "e":
		writeEncodedImg(inputImgName, outputImgName, secretMsg)
	# CLEAN AND ENCODE
	elif choice == "a":
		writeCleanImg(inputImgName, CLEAN_IMG_NAME)
		writeEncodedImg(CLEAN_IMG_NAME, outputImgName, secretMsg)
	# DECODE
	elif choice == "d":
		readEncodedImg(inputImgName)
	# DEFAULT = CLEAN
	else:
		writeCleanImg(inputImgName, outputImgName)

# Run the cli while the user has not finished
finished = False
while not finished:
	finished = cli()