Количество сохраненных точек
length(points)
BRISKPoints
| KAZEPoints
| MSERRegions
| ORBPoints
| SURFPoints
| cornerPoints
| detectBRISKFeatures
| detectFASTFeatures
| detectHarrisFeatures
| detectKAZEFeatures
| detectMSERFeatures
| detectMinEigenFeatures
| detectORBFeatures
| detectSURFFeatures
| extractFeatures
| matchFeatures