Open CV cv2.bitwise_and() function

[rickyw2777]

My question is about python and Open CV. Here is my code:

import cv2
import numpy as np
 
# read image
img = cv2.imread(r"C:\Users\asus\Desktop\20230104200344_6edae.thumb.1000_0.jpg")
# Create a mask the same size as the image
mask = np.zeros(img.shape[:2], dtype=np.uint8)
# Create a circular mask with a radius of 100 and the center at the center of the image.
mask = cv2.circle(mask, (img.shape[1]//2, img.shape[0]//2), 100, 100, -1)
# Perform bitwise operations on the image and mask
masked_img = cv2.bitwise_and(img, img, mask=mask)
 
cv2.imshow('image', img)
cv2.imshow('mask', mask)
cv2.imshow('masked_image', masked_img)
cv2.waitKey(0)
cv2.destroyAllWindows()

I want to ask about this line particularly:mask = cv2.circle(mask, (img.shape[1]//2, img.shape[0]//2), 100, 100, -1).It creates a grey circle on a black background. What if I change it to mask = cv2.circle(mask, (img.shape[1]//2, img.shape[0]//2), 100, 255, -1) so it creates a *white *circle. My question is, when performing bitwise and, I can see why a white color (R=255,G=255,B=255) can be translated to (11111111,11111111,11111111) so it can be used to preserve the orginal color. However, if it is grey,(R=100, G=100, B=100), namely (1100100,1100100,1100100), I can't really see why it preserves the color. Please help and name any of my misunderstanding.