I am currently working on a Raspberry Pi 4 with retropie and want to process the colours on the screen to do some cool stuff with LEDs. My Idea was to check the Linux framebuffer (/dev/fb0). It works for the command line itself, but as soon if I start a programm nothing changes, I noticed that if I echo urandom to fb0 it fills the console with random pixels but not the programm that runs on top (emulationstation).
As you might alreay expect I do not have much expirience with Linux graphics, so my Question is how I can get the pixel printed on the next or current frame. I found some stuff regarding X11 on the System but I didn't made much progress looking that way.
I hope someone can poke me in the right direction and thanks in advance.