TyperError When trying to show an image in grayscale on Python

I keep getting a TypeError: Invalid shape (825,) for image data when trying to display the image in grayscale.

import matplotlib.pyplot as plt
import matplotlib.image as mpimg
import numpy as np
import os
plt.rcParams['figure.figsize'] = [16, 8]

A = mpimg.imread('image4.jpg')
X = np.mean(A, -1)

img = plt.imshow(X)
img.set_cmap('gray')
plt.axis('off')
plt.show()