[Python] Why is the greyscale & B&W images created by Pillow giving a numpy.ndarray that has a...

Input:

import numpy as np
from PIL import Image

with Image.open("testimage.png") as img:
img.convert('L') # convert to greyscale
#img.convert('1') # convert to B&W
image_pil = np.asarray(img)
print(f'{image_pil.shape=}')


Output:

image_pil.shape=(266, 485, 3)


Question:

Why is the shape of image_pil not (266, 485) or (266, 485, 1)? I was expecting a 2D greyscale image but it gave a shape of (266, 485, 3) indicate that it is still a RGB image. Also, .convert('1') had the same outcome. Why are they not shaped(266, 485)?

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