From STAB Resources

Datatype : Mat

• Image is basically a 2d array or matrix.
• Elements can be of various sizes, like 8,16, 32 bits. Also there can be multiple channels.
• Grayscale, RGB, HSV, HSL.
• Declare a Mat as follows:

  Mat img(rows, cols,CV_<bit-depth>{U|S|F}C<no_of_channels>);

Mat Functions

a.at<int>(i,j) //access element at (i,j)
a.rows; a.cols //returns no of rows, cols
a.row(i); //access to ith row as another Mat
a.zeros(rows,cols,CV_8U); //mat full of zeros
a.rowRange(i,j); //access rows from i to j as another Mat
a.t(); or a’; //transpose
a.clone(b); //full copy
a.convertTo(b,CV_32F); //change type
Operations like +,-,* work with usual matrix rules
a.mul(b); //element wise multiplication
//other usual matrix operations are available, you can look have a look at the reference.