OpenCV is a C library for real time image processing. Its license is BSD.
OpenCV package includes functions to integrate it better with U++ and the necessary libraries.
To install it please remember to set "Build methods" menu:
PATH - executable directories
To ease the install there is here a packaged 2.2.0 version (OpenCV_2_2_0 plugin_BSD.7z) with the basic folders. Just download and copy it in your /uppsrc/plugin folder.
There is also a sample package (OpenCV_demo) to ease even more its use for U++ users. It uses the Hough Transform to detect straight lines in an image.