Finding the most common color/value in a matrix

Happy if they're useful to someone else.

Once you have the texture converted to CIE-L*ab you can iterate through the image and use one of the color delta formulas on this page to do comparisons:

http://www.easyrgb.com/index.php?X=DELT

More info on color difference measurements here:
http://en.wikipedia.org/wiki/Color_difference

I experimented with both the Delta E 1994 and Delta E 2000 methods, and found the 1994 algorithm to be closer to my own perception, especially when playing with tolerance levels. All of the listed methods require pre-processing to CIE-L*ab, which was the motivation behind the shaders.

I did the binning in Java, through what I euphemistically call a "lazy attractor" approach - anything that was within an adjustable tolerance of a previously observed color was grouped and then averaged to create a composite L*ab value. The larger the composite group, the higher up the comparison list it traveled, so it had a higher likelihood of ensnaring incoming pixels.

My "bins" were wrappers around an ArrayList, so I could collect the L*ab colors and eventually output a histogram that showed the color (converted back to RGB using the reverse shaders) and its relative weight.

This is unfortunately not a realtime process, and I did have to down-rez my source images to get reasonable performance, but the results were promising. I'm sure someone more clever could come up with a way to speed this up to the point that it could be used realtime - it was something I threw together fairly quickly.

If there's interest I may be able to clean up the Java code and post, but not sure when I'll have time to do that. I figured I'd release the shaders and see what you all might come up with.