Computing a homography between two images
The second recipe of this chapter showed you how to compute the fundamental matrix of an image pair from a set of matches. Another mathematical entity exists that can be computed from match pairs: a homography. Like the fundamental matrix, the homography is a 3x3 matrix with special properties and, as we will see in this recipe, it applies to two-view images in specific situations.
Let's consider again the projective relation between a 3D point and its image on a camera that we introduced in the first recipe of this chapter. Basically, we learned that this relation is expressed by a 3x4 matrix. Now, if we consider the special case where two views of a scene are separated by a pure rotation, ...