Haar-like features

Haar-like features use filters to detect regions containing areas of different image contrast – brightness and darkness in an image.

It was first designed for use in face detection, and can be very fast and effective provided you are able to select the right filters for your task.

This video explains the process in overview. For more information on the classic Viola Jones face detection algorithm, see the reference below.

P. Viola and M. Jones, “Rapid object detection using a boosted cascade of simple features,” Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001, Kauai, HI, USA, 2001, pp. I-I, doi: 10.1109/CVPR.2001.990517