Value of the hessian (can be used to approximately estimate the feature strengths; see also params.hessianThreshold.
publicfloathessian
리턴
float
laplacian 공개적으로 프로퍼티
-1, 0 or +1. sign of the laplacian at the point. can be used to speedup feature comparison (normally features with laplacians of different signs can not match)