Reading pixels from the screen?

Question

linux

What are the means for reading pixels from the screen?
Under linux and under windows.
And in OpenGL it is possible to read the frame buffer, is it possible to read everything that is displayed on the screen with it? Or just what OpenGL itself outputs?

Answer 1

On Windows it can be done like this .

Answer 2

On X11, you can use GetImage. Kind of like taking a screenshot.

Answer 3

Judging by the description, you are doing ambilight or something like that. Look at ready-made implementations, since amateur projects are usually always open. For example, there is an article on Habré .