Fast implementation of generalised median filter

The vector median filter (VMF) is a widely used means of eliminating impulse noise in colour images, and has the advantage of largely eliminating colour bleeding. The generalised median filter (GMF) has the capability for eliminating even more noise than the VMF, while not being targeted quite so specifically at colour bleeding. Ways of implementing the GMF are demonstrated so that it runs sufficiently rapidly to make it a useful alternative to the VMF, thereby opening the way for much wider use of this highly effective type of filter