Im sorry if it is a weird question, but I cant seem to find an answer for this. What does the signal going to the screen look like in more abstract sense? Does it code the values of each pixel in a huge matrix, is it a computational stream that instructs the screen what to present?
In other words, can I grab this signal by a "listening" device for example and deconstruct it with algorithms? Not just grab the signal and present it on another screen. For example, if it is a matrix of pixel values, then I can run face recognition algorithms for example, to see if the signal sent to the computer is a picture of face or not.
It might also depend on the type of screen? Say that it is a LCD screen.
edit: To elaborate, if I wanted to take the signal sent to the screen and scan it for text (NSA style), could I? If so, what should I know of the signal that Im collecting to actually do this? Disclaimer: Im not interested in spying on anyone.