from PIL import Image
import random

def modify_pixel(pixel, plane, bit, modifier):
	m = modifier * (2 ** (7 - bit))
	r = pixel[0] + m if plane == 0 else pixel[0]
	g = pixel[1] + m if plane == 1 else pixel[1]
	b = pixel[2] + m if plane == 2 else pixel[2]
	return (r, g, b)

# Choose the configurations
key = 4362
colourPlane = 0 # 0 is red, 1 is green, 2 is blue
significantBit  = 7 # 7 is the least significant bit, 0 is the most
coverImage = "img/flowers.bmp"
secret = "To be, or not to be: that is the question: Whether 'tis nobler in the mind to suffer The slings and arrows of outrageous fortune, Or to take arms against a sea of troubles, And by opposing end them? To die: to sleep; No more; and by a sleep to say we end The heart-ache and the thousand natural shocks That flesh is heir to, 'tis a consummation Devoutly to be wish'd. To die, to sleep; To sleep: perchance to dream: ay, there's the rub; For in that sleep of death what dreams may come When we have shuffled off this mortal coil, Must give us pause: there's the respect That makes calamity of so long life; For who would bear the whips and scorns of time, The oppressor's wrong, the proud man's contumely, The pangs of despised love, the law's delay, The insolence of office and the spurns That patient merit of the unworthy takes, When he himself might his quietus make With a bare bodkin? who would fardels bear, To grunt and sweat under a weary life, But that the dread of something after death, The undiscover'd country from whose bourn No traveller returns, puzzles the will And makes us rather bear those ills we have Than fly to others that we know not of? Thus conscience does make cowards of us all; And thus the native hue of resolution Is sicklied o'er with the pale cast of thought, And enterprises of great pith and moment With this regard their currents turn awry, And lose the name of action.--Soft you now! The fair Ophelia! Nymph, in thy orisons Be all my sins remember'd!"

# Read the cover-image data
image = Image.open(coverImage)
dimensions = image.size # dimensions[0] is width, dimensions[1] is height
pixels = image.load() # pixels[0,0] returns a list of the (R,G,B)-values of the pixel at position (0,0) (top left origin)

# Determine the pixel embedding order
shuffledIndices = list(range(0, dimensions[0] * dimensions[1])) # generates a list of the numbers from 0 to the number of pixels in the cover-image
random.seed(key)
random.shuffle(shuffledIndices) # re-orders the list using the key to seed the randomness

# Convert the secret into ASCII bits
# Prepend the length of the secret to it to aid extraction
sbits = "".join(format(ord(char), "b").zfill(7) for char in secret)
lbits = format(len(secret), "b").zfill(14)
bits = lbits + sbits

# Embed the secret bits into the re-ordered pixels in the chosen colour plane
for i in range(len(bits)):
	x = shuffledIndices[i] % dimensions[0]
	y = int(shuffledIndices[i] / dimensions[0])
	p = format(pixels[x, y][colourPlane], "b").zfill(8)
	
	# If the existing value is 0, only change it if the secret bit is 1
	if p[significantBit ] == "0":
		if bits[i] == "1":
			pixels[x, y] = modify_pixel(pixels[x, y], colourPlane, significantBit , 1)
	# If the existing value is 1, only change it if the secret bit is 0
	else:
		if bits[i] == "0":
			pixels[x, y] = modify_pixel(pixels[x, y], colourPlane, significantBit , -1)

# Output the stego-image
image.save("stego-image.bmp")