ORB

ORB (Oriented FAST and Rotated BRIEF) (RRKB11) combines the FAST keypoint detector with the BRIEF descriptor, modified to be rotation-invariant. Since FAST provides no orientation information, ORB computes it by determining the centroid of the brightness within the patch surrounding the keypoint: the vector connecting the point to the centroid is rigid under rotations and sufficiently robust to illumination changes.

Using this angle, ORB rotates the BRIEF pattern (using precomputed rotated patterns, for example by quantizing the full angle into 30 sectors) to generate a rotation-robust binary descriptor known as rBRIEF. In addition, applying FAST and BRIEF at different levels of an image pyramid also provides scale invariance.

ORB offers accuracy comparable to SIFT and SURF, but with significantly higher speed and, above all, without patent restrictions.