Color histogram

I just sat down to take another look at my 1 million faces project.  At some point I start using these images to create some sort of visualisation based on color, texture roughness, face position, pose etc... I just created some code which calculates a color histogram and has two ways to compare them: Chi Square and the correlation method, kindly borrowed from openCV.  At this moment I've got the basics which will get me started to create some basic structureing of the images.