The Android app Effect-Camera implements a camera that performs real time rendering on the preview using OpenGL (ES). Next to the basic image processing pipeline, there are already several OpenGL filters implemented. This includes basic filters like grayfilter, sepiafilter and negativefilter up to advanced techniques like real time edge detection or image overlays. Moreover, you can (for most of the filters) tune brightness, contrast and saturation both hard and software side. The project is still on-going and there are several tasks left. I hope you enjoy either. I captured some exemplary screenshots: