A robust variable length nonlinear filter for edge enhancement and noise smoothing

Most of the recent work in nonlinear order statistic filters has focused on smoothing and preserving the details in digital images. However, in many image analysis and computer vision applications, where edges are being used as primary features, edge enhancement becomes an essential attribute of preprocessing filters. Moreover, the human visual system is also very sensitive to this feature. Majority of the most frequently used filters, such as median and its extensions do not posses this property; median filters tend to preserve any monotonic degradation of the edge and therefore, are not capable of enhancing blurred or ramp edges. In this paper we present a variable length robust nonlinear filter which has the capability to both sharpen the edges and smoothing out the noise. Experimental results on real images are also provided.