Image Watermarking

get_ipython().ast_node_interactivity = 'all'
import os
import matplotlib.pyplot as plt
import numpy as np
import matplotlib
import math
from PIL import Image
matplotlib.rcParams['figure.dpi'] = 150
matplotlib.pyplot.rcParams["figure.figsize"] = (10, 10)

def imshow(i):
    plt.imshow(i, cmap="gray")

def fft2(i):
    return np.fft.fftshift(np.fft.fft2(img))

def ifft2(i):
    i = np.fft.fftshift(i)
    i = np.fft.ifft2(i)
    return i

def jpegify(img):
    i = Image.fromarray(np.uint8(img))
    i.save("/tmp/test.jpg")
    return np.array(Image.open("/tmp/test.jpg").convert("L"))

img = Image.open("/home/leo/snowman.jpg")
img = img.resize((img.width // 4, img.height // 4))
img = img.convert("L")
img = np.array(img)

imshow(img)

fft = fft2(img)

imshow(np.log(np.abs(fft)))

imshow(np.abs(ifft2(fft2(img))))

fft = fft2(img)

center = np.array([img.shape[0] // 2, img.shape[1] // 2])

for y in range(img.shape[0]):
    for x in range(img.shape[1]):
        p = np.array([y, x])
        dist = np.linalg.norm(center - p)
        
        if abs(center[0] - y) > 20 and abs(center[0] - y) < 45 and abs(center[1] - x) > 20 and abs(center[1] - x) < 45:
            fft[y][x] = 1+0j

imshow(np.log(np.abs(fft)))

img = ifft2(fft)

for _ in range(4096):
    img = jpegify(np.abs(img))

imshow(np.log(np.abs(fft2(img))))

imshow(img)