在鼠标处理中打开CV标志和参数

Question

这是我编写的一些代码，用于通过右键单击来获取左键单击和BGR通道值的坐标。我只想知道，为什么在flag函数中使用param和click_event参数很重要？ flag和param如何工作？

import numpy as p

import cv2

img = np.zeros([512,512,3], np.uint8)

cv2.imshow('image', img)

def click_event(event, x, y, flags, param):

    if event == cv2.EVENT_LBUTTONDOWN:

        print(x, ',', y)

        font = cv2.FONT_HERSHEY_SIMPLEX

        strxy = str(x)+ ',' + str(y)

        cv2.putText(img, strxy, (x,y), font, 1, (0,255,255), 2)

        cv2.imshow('image', img)

    if event == cv2.EVENT_RBUTTONDOWN:

        blue = img[y, x, 0]

        green = img[y, x, 1]

        red = img[y, x, 2]

        font = cv2.FONT_HERSHEY_SIMPLEX

        strxy = str(blue) + ',' + str(green) + ',' + str(red)

        cv2.putText(img, strxy, (x, y), font, 1, (255, 0, 255), 2)

        cv2.imshow('image', img)

cv2.setMouseCallback('image', click_event)

cv2.waitKey(0)

cv2.destroyAllWindows()