mouse.py

`import cv2
import numpy as np 

def detect_quadrant(event, x, y, flags, param):
    if event == cv2.EVENT_LBUTTONDOWN:
        if x > width/2:
            if y > height/2:
                point_bottom_left = (int(width/2), int(height/2))
                point_top_right = (width-1, height-1)
            else:
                point_top_right = (width-1, int(height/2))
                point_bottom_left = (int(width/2), 0)
        else:
            if y > height/2:
                point_top_right = (int(width/2), int(height/2))
                point_bottom_left = (0, height/2)
            else:
                point_bottom_left = (0,0)
                point_top_right = (int(width/2), int(height/2))

        cv2.rectangle(img,  (0,0),  (width-1,height-1), (255,255,255),  -1)
        cv2.rectangle(img, point_bottom_left, point_top_right, (0,255,0), -1)


if __name__=='__main__':
    width, height = 640, 480
    img = 255 * np.ones((height, width, 3), dtype = np.uint8)
    cv2.namedWindow('input_window')
    cv2.setMouseCallback('input_window', detect_quadrant)                   # A callback function is one that should be called when a certain condition is met. 
                                                                            # Instead of being called immediately, the callback function is called at a certain point in the future.
    while True:
        cv2.imshow('input_window', img)
        c = cv2.waitKey(1)                                              # this will say to callback that stop for 10 sec
        if c == 27:
            break
    cv2.destroyAllWindows()