title: How is the photoshop cutout filter implemented?
body: <p>Photoshop has a lot of cool <a href="http://alanwho.com/photoshop/photoshop-artistic-filters/" rel="noreferrer">artistic filters</a>, and I'd love to understand the underlying algorithms.</p>
  
  <p>One algorithm that's particularly interesting is the Cutout filter (number 2 at the link above).</p>
  
  <p>It has three tunable parameters, Number of Levels, Edge Simplicity, and Edge Fidelity.  Number of levels appears to drive a straightforward posterization algorithm, but what the other sliders do technically eludes me.</p>
  
  <p>I would think that they're doing something related to Vornoi diagrams or k-means partitionion, but poking around on wikipedia hasn't resulted in anything that maps obviously to what Photoshop is doing, especially considering how fast the filter renders itself.</p>
  
  <p>Is there any source for technical descriptions of the Photoshop filters?  Alternatively, do you have any thoughts about how this particular filter might be implemented?</p>