Artistic image filter

Efficient algorithm of an artistic image filter, similar to commonly-used image applications.

This function tries to simulate a generic image filter similar to the commonly-used filters of mobile applications like Instagram, Pixl-o-matic, Photo Illusion, Retro Camera, and so on.
The image processing used here is composed by a RGB mapping and a circular/eliptical mask which desaturates, decreases brightness levels and blurs progressively the mapped image. Loops are not used, therefore, performance is bearable.
Example of use:
I = imread('myimage.jpg');
M = imfilter_artistic(I);
imshow(M);