KLT is an implementation, in the C programming language, of a feature tracker that will hopefully be of interest to the computer vision community. The tracker is based on the early work of Lucas and Kanade [1] and was developed fully by Tomasi and Kanade [2], but the only published, readily accessible description is contained in the paper by Shi and Tomasi [3]. Recently, Tomasi proposed a slight modification which makes the computation symmetric with respect to the two images; the resulting equation is fully derived in the unpublished note by Birchfield [4].
Briefly, good features are located by examining the minimum eigenvalue of each 2 by 2 gradient matrix, and features are tracked using a Newton-Raphson method of minimizing the difference between the two windows. Multiresolution tracking allows for even large displacements between images. Currently, the affine computation that evaluates the consistency of features between non-consecutive frames [3] is not implemented.