Book Image

Mastering OpenCV Android Application Programming

Book Image

Mastering OpenCV Android Application Programming

Overview of this book

Table of Contents (16 chapters)
Mastering OpenCV Android Application Programming
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
6
Working with Image Alignment and Stitching
Index

Fast Retina Keypoint


Fast Retina Keypoint (FREAK) proposes a robust descriptor to uniquely identify keypoints and in the process, require less computation time and memory. FREAK has been inspired by the human retina.

A retinal sampling pattern

FREAK proposes to use the retinal sampling grid, which is also circular, with the difference of having higher density of points near the center. The density of points drops exponentially as we move away from the center point. This is similar to BRISK, except for the exponential decrease.

Each keypoint needs to be smoothed to be less sensitive to noise. Unlike BRIEF and ORB, which use the same kernel for all points, FREAK uses a different kernel for each keypoint. The radius of the Gaussian kernel is proportional to the value of σ.

Retinal sampling pattern

FREAK follows ORB's approach and tries to learn about the pairs by maximizing the variance of the pairs and taking pairs that are not correlated, so as to provide maximum information on each keypoint...