For my two ofx-Addons project, I used the ofx-OpenCV add-on and the ofx-UI add-on. I wanted to work with the OpenCV add-on and make a program that allowed the user to do a bunch of things with the UI overlay over the video. I added some basic functionality to the UI like have toggle buttons, states and switches. There are function keys for making the UI go away or making the overlay darker. The user controls everything that goes on in the UI. The background is OpenCV that uses your webcam to capture the video.
Combining these two libraries can lead to a bunch of cool applications. One can have various UI functions to change the video modes (black and white to pixel to face tracking video). We can have toggle switches to switch between video modes. Generally, the UI can make controlling the video options Open-CV gives by a novice user very simple.
Source code: https://github.com/safinahali/congenial-winner