I need to apply a bitmap effect on the screen image before it's displayed on screen. This must be done in real time. Ideally, this should work with all graphical output, including games. User must be able to use the computer as normal.
Can you advise me what is the best way to do this under linux? Can it be done in x11? Or display driver needs to be modified?
Note: this is a repost of the question where I asked the same thing under windows (I gave up): How to apply an effect on screen image in Windows on the fly?
Thanks!