What are features?

Features are specific patterns that are unique and can be easily tracked and compared. Good features are those that can be distinctly localized. The following image shows the different kind of features:

Explains types of features

In the preceding image, patch A is a flat area and is difficult to locate precisely. If we move the rectangle anywhere within the box, the patch contents remain the same. Patch B, being along an edge, is a slightly better feature because if you move it perpendicular to the edge, it changes. However, if you move it parallel to the edge, it is identical to the initial patch. Thus, we can localize these kind of features in at least one dimension. Patch C, being a corner, is a good feature because on moving the rectangle in any direction, the contents of the patch change and can be easily localized. Thus, good features are those which can be easily localized and thus are easy to track.

In the previous chapters, we have seen some of the edge and corner...