When calling filter2D and sepFilter2D, I want to use a constant border, which I do by providing BORDER_CONSTANT for the "borderType" parameter as specified in the documentation (http://opencv.itseez.com/modules/imgproc/doc/filtering.html?highlight=gaussianblur#filter2d).
However, I do not see how I can specify WHAT I want that constant value to be. How do I achieve this?