Edge versus contrast estimation of morphological filters

Abstract

The estimation properties of morphological filters are considered in terms of edge localization and grey level contrast preservation in two-dimensional spaces. It is shown that, at least in practice, a compromise between these two characteristics has to be made. In a first step, morphological filters are compared with linear and median filters. It is concluded that an efficient edge localization can be achieved with morphological filters with reconstruction but not with median filters or with morphological openings or closings with structuring elements. In the case of strong noise, the good edge preservation provided by the reconstruction filters is obtained at the expense of contrast estimation. In order to be able to tune this tradeoff, a new type of morphological filter, called filters with partial reconstruction is proposed and studied.