Android Floating Window and Scan

I like to implement an app which is scanning the screen and analyse the resulting picture. I found an old community discussion with the result, that it is not possible. Has the situation changed?

My idea was to create my ionic application, export it to android, create an android floating window to create a button which is visible when reading text from a website or whatever, scan the screen and pass the resulting string to the ionic app. OR Do everything with just ionic.

Thanks for help!