This tutorial shows how to work with selection area (also known as Region of Interest, or ROI) in a sample ASP.NET Web Forms application that will apply a negative filter on a particular area.
The starting point of this tutorial is the application you have at the end of Your first DocuVieware ASP.NET Web Forms page, it is a prerequisite so if you do not have it, please follow this tutorial first.
You are going to add three buttons above the DocuVieware™ control, one will simply output the coordinates of the selection area (if any), another one will clear it and finally the last button will apply a negative filter on the selected area.
1. Display the ROI coordinates
2. Clear the ROI
3. Apply the negative filter on the ROI