Steamgifts Steganography Add.Py

from PIL import Image, ImageFilter

def get_num_bits_secret():
    return 1

#Read host image
visible = Image.open( 'top.png' )
#Read the hidden image
secret = Image.open( 'bot.png' )

num_bits_secret = get_num_bits_secret()

def combine(visible, secret):

    width1, height1 = visible.size
    width2, height2 = secret.size

    if width1 != width2 or height1 != height2:
        print("the two images don't have the same dimensions")
        raise 1

    ret = visible.copy()
    # iterate through the pixels
    for i in range(width1):
        for j in range(height1):

            # bigpixel is the pixel from the host image and smallpixel is the pixel from the hidden image.
            bigpixel = list( ret.getpixel((i,j)) )
            smallpixel = list( secret.getpixel((i,j)) )

            # iterate through the 3 color components (RGB).
            for c in range(3):
                bigvalue = bigpixel[c]
                smallvalue = smallpixel[c]

                # "<<" and ">>" are bit shifting operators. They make a number lose binary digits at the right side, or add zeros at the right side.
                # e.g.: x >> 2, makes x lose two bits from the end (it's like dividing by 2^2 and taking only the quotient)
                # e.g.: x << 2, adds two 0 bits to the right of x (it's like multiplying by 2^2)

                # here, we just replace the last num_bits_secret bits in bigvalue with zeros.
                bigvalue = ((bigvalue >> num_bits_secret) << num_bits_secret)

                # we keep only the first num_bits_secret from the left side of smallvalue.
                smallvalue = (smallvalue >> (8 - num_bits_secret))

                # we add them together to get the combined number
                newvalue = bigvalue + smallvalue
                bigpixel[c] = newvalue

            # place the modified pixel back into the copy of the host image.
            ret.putpixel((i,j), tuple(bigpixel))

    return ret

combined = combine(visible, secret)
combined.save('combined.png')
# combined.show()