import cv2 as cv
import numpy as np

img=np.ones((512,512))

def draw_circle(event,x,y,flags,param):
    if event==cv.EVENT_LBUTTONDOWN:
        cv.circle(img,(x,y),20,0,-1)

cv.namedWindow('show_img')

cv.setMouseCallback('show_img',draw_circle)
while(1):
    cv.imshow('show_img',img)
    pressedKey=cv.waitKey(5)
    if pressedKey==ord('q'):
        break
    elif pressedKey==ord('s'):
        cv.imwrite("mouse_draw_circle.jpg",img);
        print("save success")
cv.destroyAllWindows()