Just a small snippet to test normalization

testing_gray_and_black.py

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.image as mpimg

img = mpimg.imread("D:\\Projetos\\Cinza\\teste.jpg")

gray = 0.299 * img[:, :, 0] + 0.587 * img[:, :,1] + 0.114 * img[:, :,2]
gray = gray.astype(np.uint8) # garantindo valores inteiros

limit = 127
black = np.zeros_like(gray)
for i in range(len(gray)):
    for j in range(len(gray[i])):
        black[i][j] = 1 if gray[i][j] > limit else 0

plt.imshow(gray, cmap='gray')
plt.show()

plt.imshow(black, cmap='gray')
plt.show()

print(img.shape)
print(gray.shape)