Learning OpenCV 4 Computer Vision with Python 3 - Third Edition

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 pixels marked as brighter or darker.

FAST also uses a high-speed test, which can sometimes determine that a neighborhood is not a corner by checking just 2 or 4 pixels instead of 16. To understand how this test works, let's take a look at the following diagram, taken from the OpenCV documentation:

Here, ...