Open GL + Applying Brightness on the Image + Undo Brightness operation

I am working on one module of application. in this I need to perform brightness operation on the image [ I have done this using OpenGL ES ].

Now I am stuck on how to revert back this brightness operation if in between user clicks "Cancel". As I am 开发者_开发问答drawing on same layer for brightness operation.

I am new to OpenGL and might missing some basics. can anyone help me to give me some direction regarding same.

Thanks,

Sagar

I have achieved this using two separate UIView. one for actual displaying and second one for OpenGL View. so whenever user clicks done I pass the UIImage from OpenGL view else on cancel shows the previous image.