import cv2

def draw_rectangle(event,x,y,flags,param):
    w,h =img.shape[::-1]
    if (event == cv2.EVENT_LBUTTONDOWN and x<=10 and y<=10) or (event == cv2.EVENT_LBUTTONDOWN and x>=w-10 and y>=h-10):
            img1 = cv2.rectangle(img, (200, 200), (510, 128), (0, 255, 0), 3)
            img1 = (255-img1)

img = cv2.imread('obiekty.png',0)
cv2.namedWindow('image')
cv2.setMouseCallback('image',draw_rectangle)
while(1):
    cv2.imshow('image',img)
    if cv2.waitKey(20) & 0xFF == 27:
        break
cv2.destroyAllWindows()