I'm using "OCR" in my screensaver mod. Well not really, it just looks for a specific pixel pattern in a single line of pixels.
Described here:
https://www.mobileread.com/forums/sh...35#post3165835
Didn't always work for everyone, also because of other reasons (has to be done as device goes to sleep, not much time, slow implementation, then the RGBA change etc., and just about every firmware update changed the font rendering)