Fast Gaussian quantization

Fast Gaussian blur + Image quantization = Fast Gaussian quantization.

This works followed closely the work I have done on image voronoization. The Codegolf thread that initiated the aforementioned project links another related Codegolf thread "Paint by Numbers", which I again wanted to try.

The answer provided by DavidC is a Mathematica code that perform a Gaussian blur step then an image quantization. Pretty simple and giving nice results ! I decided to port the exact same routine to C++, using my implementation of the fast Gaussian blur approximation by IvanK (see details here and my code here) and a classic K-Means pass for image quantization.

Here are the the results with various blur radiis (R) and number of colors after quantization (K):

|R\K|4|16|64|256| |:-:|:-:|:-:|:-:|:-:| |0||||| |1||||| |2||||| |4||||| |8||||| |16|||||