Using ORB with FAST features and BRIEF descriptors
If SIFT is young, and SURF younger, ORB is in its infancy. ORB was first published in 2011 as a fast alternative to SIFT and SURF.
The algorithm was published in the paper ORB: an efficient alternative to SIFT or SURF, available in PDF format at http://www.willowgarage.com/sites/default/files/orb_final.pdf.
ORB mixes the techniques used in the FAST keypoint detector and the BRIEF keypoint descriptor, so it is worth taking a quick look at FAST and BRIEF first. Then, we will talk about brute-force matching – an algorithm used for feature matching – and look at an example of feature matching.
FAST
The Features from Accelerated Segment Test (FAST) algorithm works by analyzing circular neighborhoods of 16 pixels. It marks each pixel in a neighborhood as brighter or darker than a particular threshold, which is defined relative to the center of the circle. A neighborhood is deemed to be a corner if it contains a number of contiguous...
