We saw how to track different objects in a scene and how to make a human interface using them, but we did not see a more generalized approach. When an object changes its position, it moves through a scene and it is interesting to estimate the overall movement of the scene. Here, we will introduce the concept of optical flow, and will see how to use it for object tracking. In the first part, we will focus on the theory and then present two wonderful examples of the optical flow usage. Finally, we will create a simple gesture application.
There are many definitions of optical flow, the main one is: it is the change in structured intensities of an image due to relative motion between the eyeball (camera) and the scene (http://www.scholarpedia.org/article/Optic_flow). According to another definition, it is the distribution of the apparent velocities of objects in an image (http://www.mathworks.com/discovery/optical-flow.html). To...