I started porting some filters from various sources into Processing. There's just two examples for now but more will come.
You can get them from this Github repository
Edit (may 27th 2015): The filters now have their own repository, complete with a proper readme.
Barrel Blur Chroma
Source: https://www.shadertoy.com/view/XssGz8
Contrast Saturation Brightness
Source: http://mouaif.wordpress.com/?p=94
Have fun and filter responsibly :)