A while ago I was working on a sample app to demonstrate basic image editing abilities using ColorFilter to adjust an image brightness, contrast and saturation.
Color filters are great, but they are comparatively slow on large images, while looking for better options I learned that we could use Effects that are available in Android API Level 14
The effects in Android uses GPU and OpenGL textures to perform all the processing for maximum performances. The EffectFactory provides the list of various effects that can be applied to an image not just basic adjustments like brightness and contrast.
I have ported one of the Google’s sample to Xamarin.Android to demonstrate these effects, this should be a useful getting started sample for developers like me :)
The GitHub repository includes the full solution for the app in the screenshot if you want to run from it: monodroid-samples
My lame blog 
Hi this code is awsome! saved me tons of time! I have a question though, I am struggeling trying to save the GlSurface view modified image to a bitmap I have tried porting the code from here http://stackoverflow.com/questions/7554553/cocos2dhow-to-create-bitmap-from-glsurfaceview but i cant get it to work… do you have any ideas?
Thanks
Amit
Good to hear my code helped you save time :)
Do you get any errors porting SO code? I would suggest you post what you have tried so far at http://forums.xamarin.com/ it would be easy to understand/debug it, and other developers can pitch in their ideas too
Thanks for the quick reply! I have posted it indeed – here http://forums.xamarin.com/discussion/9139/saving-glsurface-view-to-bitmap-monodroid?new=1 If you could look at what I did I will be so happy.
Thanks again!