将Mat元素（uchar）写入.csv

Question

I want to output the content of a Mat object (OpenCV uchar) to a .csv file.

Right now, I am able to write ints and doubles and even (it seems) the uchars but when opening the csv in Excel, the uchar are interpreted as characters so I can't inspect the values. So I tried to cast them to a string before saving them to csv, but it failed.

My code so far:

Ofstream Datalogger(path);
// Some code

for (int i = 0; i< vector1.size();i++)
        {
            Datalogger << i << ";"
                << vector1[i].someint << ";"     
                << vector1[i].somedouble << ";" 

            const uchar* Mi = Mat1.ptr<uchar>(i);
            for(int k = 0; k < Mat1.cols; k++)
            {               
                std::string descr( Mi[k]);
                Datalogger << descr << ";" ; 
            }        
            Datalogger << endl;
        }

But the error code is:

1   IntelliSense: no instance of constructor "std::basic_string<_Elem, _Traits, _Alloc>::basic_string [with _Elem=char, _Traits=std::char_traits<char>, _Alloc=std::allocator<char>]" matches the argument list argument types are: (const uchar)

Which probably means the string descr() cannot accept uchars.

Any idea how to log the content to .csv AND being able to see the numerical value of the uchar instead of it being interpreted as a special character by Excel?

Answer 1

Ok, since don't really need to have a string and only to be able to read the numerical value in Excel, I simply did a cast to an int.

for (int i = 0; i< vector1.size();i++)
        {
            Datalogger << i << ";"
                << vector1[i].someint << ";"     
                << vector1[i].somedouble << ";" 

            const uchar* Mi = Mat1.ptr<uchar>(i);
            for(int k = 0; k < Mat1.cols; k++)
            {               
                int descr = int( Mi[k]);
                Datalogger << descr << ";" ; 
            }        
            Datalogger << endl;
        }

Answer 2

cv::format() may be also useful:

cv::Mat M = cv::Mat::ones(3, 3, CV_8UC3);
std::cout << cv::format(M, "csv") << std::endl;

There are also some other options to print/format mat to the output:
http://docs.opencv.org/doc/tutorials/core/mat_the_basic_image_container/mat_the_basic_image_container.html#output-formatting