Opencv 中 Mat中元素的值读取方法总结

Mat img1 = imread(filename,IMREAD_GRAYSCALE);  
   for( size_t nrow = 0; nrow < img1.rows; nrow++)  
   {  
       for(size_t ncol = 0; ncol < img1.cols; ncol++)  
       {  
           uchar val = mat_CV_8UC1.at<uchar>(nrow,ncol);      
       }  
   }  

Mat img2 = imread(filename,IMREAD_COLOR);  
   for( size_t nrow = 0; nrow < img2.rows; nrow++)  
    {  
       for(size_t ncol = 0; ncol < img2.cols; ncol++)  
       {  
           Vec3i bgr = mat_CV_8UC3.at<Vec3b>(nrow,ncol);//用Vec3b也行  
           cout   << "("<<bgr.val[0]<<","  
                   <<bgr.val[1]<<","  
                   <<bgr.val[2]<<")";  
       }  
       cout << endl;  
    }  

for( size_t nrow = 0; nrow < img3.rows; nrow++)  
    {  
        uchar* data = img3.ptr<uchar>(nrow);  
       for(size_t ncol = 0; ncol < img3.cols * img3.channels(); ncol++)  
       {  
            cout << int( data[ncol] ) ;  
       }  
       cout << endl;  
    }  

Mat img4 = imread(filename,IMREAD_GRAYSCALE);
MatIterator_<uchar> it = img4.begin<uchar>(), it_end = img4.end<uchar>();  
   for(int cnt = 1; it != it_end; ++it)  
    {  
        cout << ( int(*it) ) ;  
        if( (cnt++ % img4.cols) ==0 )  
            cout << endl;       
    }  

Mat img5(rows, cols,CV_8U, Scalar(0));
for( size_t nrow = 0; nrow < img5.rows; nrow++)  
for(size_t ncol = 0; ncol < img5.cols; ncol++)
    {  
       cout<<(int)(*(img5.data+img5.step[0]*nrow+img5.step[1]*ncol));
    }  

5、补充：在使用 at 函数的情况下需要预先知道Mat变量中存储的元素类型，如果类型不匹配就会出现读错误。所以可以采用c++  boost库中的BOOST_TYPEOF来获取图像的元素数据类型。例：

Mat img6 = imread(filename);
typedef BOOST_TYPEOF(*img6.data) ElementType
for( size_t nrow = 0; nrow < img1.rows; nrow++)  
   {  
       for(size_t ncol = 0; ncol < img1.cols; ncol++)  
       {  
        cout<<mat_CV_8UC1.at<ElementType>(nrow,ncol);      
       }  
   }