The most commonly seen object in our lives is a human face. We interact with people everywhere even when we do not meet them in person; we write a lot of messages via social networks, such as Twitter and Facebook, or e-mails and text messages using our phones. Face detection and tracking has many applications. In some cases, you might want to create a human computer interface, which will take the head position as an input or, more likely, you might want to help your users with tagging their friends. Actually, there are a lot of face detection libraries, which are written on JavaScript; these outnumber the libraries that focus on image processing itself. This is a good opportunity to choose the library that you really need. In addition to face detection, many libraries support face particle recognition and recognition of other objects.
In this chapter, we will focus on the JSFeat (http://inspirit.github.io/jsfeat/), tracking.js (http:...