*May 2020*

tl;dr: A summary of classical keypoints and descriptors.

- BRIEF: Binary Robust Independent Elementary Features
`ECCV 2010` - The sampling pattern is randomly generated but the same for all image patches. In openCV, the sampling sequence is pre-fixed.
- patch window is 31 x 31.

- blog review on BRIEF descriptor

- ORB: an efficient alternative to SIFT or SURF
`ICCV 2011` - Sampling pairs should have
**uncorrelation and high variance**to ensure the fixed length would encode maximum discriminative information. - ORB is improved BRIEF:
- ORB uses an orientation compensation mechanism, making it rotation invariant.
- ORB learns the optimal sampling pairs, whereas BRIEF uses randomly chosen sampling pairs.

- blog review on ORB

- Summaries of the key ideas