Detecting planar targets in an image

In the previous recipe, we explained how homographies can be used to stitch together images separated by a pure rotation to create a panorama. In this recipe, we also learned that different images of a plane also generate homographies between views. We will now see how we can make use of this fact to recognize a planar object in an image.

How to do it...

Suppose you want to detect the occurrence of a planar object in an image. This object could be a poster, painting, signage, book cover (as in the following example), and so on. Based on what we learned in this chapter, the strategy would consist of detecting feature points on this object and to trying to match them with the feature points...