OpenCV获取鼠标左键点击位置图像的像素值

#include<opencv2\opencv.hpp>
#include<iostream>
using namespace std;
using namespace cv;
void on_mouse(int EVENT, int x, int y, int flags, void* userdata);
void main()
{
 namedWindow("【display】");
 Mat src;
 src = imread("F:\\lena_rgb.jpg");
 //cvtColor(src, src, COLOR_RGB2GRAY);
 setMouseCallback("【display】", on_mouse,&src);
 //以40ms刷新显示
 while (1)
 {
  imshow("【display】", src);
  waitKey(40);
 }



}

void on_mouse(int EVENT, int x, int y, int flags, void* userdata)
 {
  Mat hh;
  hh = *(Mat*)userdata;
  Point p(x, y);
  switch (EVENT)
  {
   case EVENT_LBUTTONDOWN:
   {

    printf("b=%d\t", hh.at<Vec3b>(p)[0]);
    printf("g=%d\t", hh.at<Vec3b>(p)[1]);
    printf("r=%d\n", hh.at<Vec3b>(p)[2]);
    circle(hh, p, 2, Scalar(255),3);
   }
   break;

  }




 }