cv::Mat of large integers

Question

I am struggling with putting large integers, such as 2942584, in a cv Mat. The only type accepting it was CV_8UC1, but it changes the value from 2942584 to 120 (well in 8 bits obviously).

But is there anyway to have the original value in a cv Mat??

Here is the simple code if it helps:

Mat matrix(6,10,CV_8UC1);
matrix.at<char>(0,0) = 2942584;
cout << (int)matrix.at<char>(0,0);

output:

120

Answer 1

When you define matrix as CV_8UC1 you define that every element must be 8 bit. That means that you can store only value from 0 to 255. If you want to use a big number you should define matrix as CV_32UC1 for unsigned integers or CV_32SC1 for signed integers. Also you should to store a value as int instead of char and read it in appropriate way.

More correct code is

Mat matrix(6,10,CV_32SC1); 
matrix.at<int>(0,0) = 2942584;
cout << (int)matrix.at<int>(0,0);

One more thing: format of the matrix element is the following

CV_<NUMBER_OF_BITS><SIGNED/UNSIGNED>C<NUMBER_OF_CHANNELS>