Ranked directional morphological filtering of impulse noise in images

In this paper, we present a hybrid rank-order/morphological filtering algorithm for removal of impulse noise. It consists of an impulse noise detector and a weighted rank-order morphological filter. For salt (pepper) noise suppression, a generalized directional opening (closing) filter is selectively used. The detection of impulse noise is easily done using the difference between the signal and its opening and closing. Simulations show that this new filter performs better than other nonlinear filters in preserving desired image features while effectively reducing impulse noise