Определите, пуст ли объект точек
detectKAZEFeatures
| detectBRISKFeatures
| detectMSERFeatures
| detectFASTFeatures
| detectMinEigenFeatures
| detectORBFeatures
| detectSIFTFeatures
| detectHarrisFeatures
| extractFeatures
| matchFeatures
| detectSURFFeatures
| MSERRegions
| SURFPoints
| BRISKPoints
| KAZEPoints
| cornerPoints
| ORBPoints
| SIFTPoints