OPENCV学习笔记2-8_Mat_类

#include <iostream>
#include "opencv2/opencv.hpp"
#include <stdio.h>
using namespace std;
using namespace cv;
int main( int argc, char* argv[] )
{
    Mat M( 600, 800, CV_8UC1 );
/*
    for ( int i = 0; i < M.rows; ++i )
    {
    //获取指针时,需要指定类型
        uchar * p = M.ptr<uchar>( i );
        for ( int j = 0; j < M.cols; ++j )
        {
            double d1 = (double) ( (i + j) % 255);
    //用at()读写像素时，需要指定类型
            M.at<uchar>( i, j ) = d1;
    //代码错误，应使用at<uchar>(),但编译时不会提醒错误
            double d2 = M.at<double>( i, j );
        }
    }
*/
   //在变量声明时指定矩阵元素类型
    Mat_<uchar> M1 = (Mat_<uchar>&)M;
    for ( int i = 0; i < M1.rows; ++i )
    {
        uchar * p = M1.ptr( i );
        for ( int j = 0; j < M1.cols; ++j )
        {
            double d1 = (double) ( (i + j) % 255);
            M1( i, j ) = d1;
            double d2 = M1( i, j );
        }
    }
    cout <<"M = "<< M <<endl;
    return(0);
}