Mask.py

import cv2 as cv
import numpy as np


img = cv.imread('105180399.jpg')

blank = np.zeros(img.shape[:2], 'uint8')
mask = cv.circle(blank, (img.shape[1]//2, img.shape[0]//2), 100, 255, -1)

masked = cv.bitwise_and(img,img, mask=mask)

cv.imshow('Masked', masked)
cv.waitKey()