cutting an image?

edit

You can do that by using the region of interest parameter.

Some sample code:

Mat original_image, first_half, second_half;
original_image = imread(location, 1);
Rect roi_first = Rect(0,0,original_image.cols/2, original_image.rows);
Rect roi_second = Rect(original_image.cols/2,0,original_image.cols/2, original_image.rows);
first_half = original_image( roi_first );
second_half = original_image( roi_second );