opencv 图片像素x,y 访问！！！

#include "opencv2/core.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"
 
#include <iostream>
 
using namespace cv;
using namespace std;
 
int main()
{
    Mat mat_src = Mat::eye(3, 4, CV_8UC1);
 
    cout << "mat_src :" << endl;
    cout << mat_src    << endl;
 
    cout << endl;
    cout << "Rows : " << mat_src.rows << endl;
    cout << "Cols : " << mat_src.cols << endl;
 
    //注: mat_src.at<float>(y, x), 下标关系为: y-x
    mat_src.at<float>(0, 2) = 2; 
    mat_src.at<float>(2, 0) = 4;
 
    cout << endl;
    cout << "mat_src :" << endl;
    cout << mat_src    << endl;
 
    return 0;
}