Yeah most of the information is lost, but if you know the font used for the text (as is the case with a screencast of a macOS window), then you can try every po

Yeah most of the information is lost, but if you know the font used for the text (as is the case with a screencast of a macOS window), then you can try every possible combination of characters, render it, and then apply the averaging, and see which ones produce the same averaged color that you see. In addition, in practice not every set of characters is equally likely --- it's much more likely for a folder to be called "documents" than "MljDQRBO4Gg". So that further narrows down the amount of trying you have to do. You are right, of course, that the bigger the group of pixels, the harder it gets: exponentially so.