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== Gaussian kernels ==

The usual way to create a Gaussian kernel is to evaluate a Gaussian function at the center of each cell:

 k[i][j] = exp(-(i²+j²)/2σ)

This usually works well, except when the kernel is thin (σ < 1). It gets worse when using our generalised kernel:

 k[i][j] = exp(-((i×cosθ-j×sinθ-dx)²+(j×cosθ+i×sinθ-dy)²)/2σ)

== Median filter ==

There are several ways to optimise a median filter.

Random links for now:
 * [http://coding.derkeiler.com/Archive/General/comp.programming/2004-10/0289.html Sliding median filter]
 * [http://iris.usc.edu/Vision-Notes/bibliography/twod268.html A shitload of papers about median filtering and its derivatives]