code.py

from PIL import Image, ImageDraw, ImageChops
import os

path = os.path.dirname(os.path.abspath(__file__))

size = (480,360)

class LCG:
    def __init__(self,m,a,c,seed):
        self.m = m
        self.a = a
        self.c = c
        self.seed = seed

    def next(self):
        while True:
            self.seed = (self.a * self.seed + self.c) % self.m
            return self.seed


def delfolder(folder):
    for i in os.listdir(os.path.join(path,folder)):
        os.remove(os.path.join(path,folder,i))

def random_image(lcg):
    im = Image.new("L",size)
    pix = im.load()

    print(lcg.seed)

    for i in range(0,im.size[1],2): # for every pixel interlaced even:
        for j in range(im.size[0]):
            dat = lcg.next()
            pix[j,i] = dat % 255
    
    for i in range(1,im.size[1],2): # for every pixel interlaced odd:
        for j in range(im.size[0]):
            dat = lcg.next()
            pix[j,i] = dat % 255

    return im


def open_image(path):
    return Image.open(path).resize(size,Image.ANTIALIAS)

def readframes(dir):
    frames = []
    for i in sorted(os.listdir(os.path.join(path,dir)),key=lambda i: int(i.replace("image","").replace(".png",""))):
        frames.append(
            open_image(os.path.join(path,dir,i))
        )
    return frames


def extractFrames(gif, folder):

    with Image.open(gif) as im:
        print(">",im.n_frames)
        for i in range(im.n_frames):
            im.seek(i)
            im.save('{}/image{}.png'.format(os.path.join(path,folder), str(i)), "PNG")


def xor(im,other):
    assert im.size == other.size

    res = Image.new("L",im.size)
    pix = res.load()

    pix1 = im.load()
    pix2 = other.load()

    for i in range(im.size[0]): # for every pixel:
        for j in range(im.size[1]):
            pix[i,j] = pix1[i,j] ^ pix2[i,j]

    return res

# 50000
def encode(intro, data, out, generator):
    frames = []
    
    introframe = open_image(intro).convert('L').resize(size)

    for i in range(10):
        frames.append(introframe)

    delfolder("images")
    extractFrames(data,"images")
    dataframes = readframes("images")

    introframe.load()
    for index,i in enumerate(dataframes):
        encodingframe = random_image(generator)
        print("combining image {}/{}".format(index+1,len(dataframes)))
        newimg = i.resize(size, Image.ANTIALIAS).convert('L')
        newimg.load()
        frames.append(xor(newimg,encodingframe))


    newframes = []
    for index,i in enumerate(frames):
        print("converting image {}/{}".format(index+1,len(frames)))
        newframes.append(i.convert("RGB"))
    frames = newframes

    print(len(frames))


    # Save into a GIF file that loops forever
    frames[0].save(out, format='GIF', append_images=frames[1:], save_all=True, duration=100, loop=0)



    # ffmpeg -i data.gif -c:v gif images/out%04d.png


def decode(inp,out, generator, ignore=1):
    delfolder("images")
    extractFrames(inp,"images")
    dataframes = readframes("images")



    frames = []

    for index,i in enumerate(dataframes[ignore:]):
        decodingframe = random_image(generator)
        
        print("restoring frame {}/{}".format(index+1,len(dataframes)))
        newimg = i.convert('L')
        newimg.load()
        frames.append(xor(newimg,decodingframe))
    
    newframes = []
    for index,i in enumerate(frames):
        print("converting image {}/{}".format(index+1,len(frames)))
        newframes.append(i.convert("RGB"))
    frames = newframes
    print(len(frames))

    frames[0].save(out, format='GIF', append_images=frames[1:], save_all=True, duration=100, loop=0)


if __name__ == "__main__":

    encode(
        os.path.join(path,"introframe.png"),
        os.path.join(path,"data4.gif"),
        os.path.join(path,"result.gif"),


        LCG((2**61)-1,13,7,424242)
    )


    decode(
        os.path.join(path,"result.gif"),
        os.path.join(path,"decodedresult.gif"),
        LCG((2**61)-1,13,7,424242),
        1
    )