Hello everybody, i want to share the Apels GammaCorrection shader originally made by Apel, this shader you can find in whole internet but it had errors in the code, which made it impossible to compile it. I only fixed the wrong end of the code, and now it can be successfully compiled via MGE XE GUI. 
So now you can use it without any errors. There are three tunable variables inside, so you can adjust it how you like. 
Enjoy :)