How do screenshots work from a software perspective

Question

How does a screenshot work from a system perspective. I've tried doing some searching, and it seems like all the sites I find are "how do I take a screenshot".

I am more interested in how the operation a screenshot works, Suppose I build my own little device that has a screen, and the data is being displayed on the screen, how would one implement a screenshot (high level, although if you want I suppose an example would be nice), on my device.

EDIT: I see that I had a request to close, I suppose this question is too hard to answer without a very specific context, and perhaps that would eventually be considered out of date, any recommendations on where to post such a question if this is not the right place?

Answer 1

This may not be helpful at all, but two of the screenshot utilities I use on a regular basis are open source and fairly short reads:

• The first is scrot, a simple command line program which takes screenshots using imlib2. Both implemented in C.
• The second is the Chrome Screen Capture app by Google, implemented in JS/C++.