Distance-weighted median filters and their application to colour images

This paper introduces a new filter based on the weighted median type of filter. The new filter employs a spatial weighting function and is intended to give improved noise suppression performance when applied to colour images. The particular advantage of the new filter is that is able to achieve an optimum balance between the improved noise ´averaging´ offered by larger windows and the increased blurring they introduce. The filter is optimised by a parameter a and reverts to the standard vector median filter (VMF) when a tends to infinity: hence it is not surprising that it is able to improve on the noise performance of the VMF. Tests show a linear weighting function to be superior to a square law weighting function with a particular set of test images.