BradLarson/GPUImage — pull request #562 by karlvr (2012-10-18 13:07:42+00:00)
Title: Levels

I've implemented a filter to reproduce the Levels filter in Photoshop et al.

This makes use of some macros by Romain Dura (http://mouaif.wordpress.com/2009/01/05/photoshop-math-with-glsl-shaders/), that are referenced in every discussion about levels and GPUImage. The macros are modified slightly to suit the shader implementation.