Why would you store the screenshot to disk, just grab what ever the compositor gives you and render it on a texture, skipping the whole disk write usage
https://blogs.windows.com/windowsdeveloper/2019/09/16/new-wa...
It's similar for both macOS and X11 (haven't looked at wayland yet)
I'm not sure why this would be so inefficient, as the screenshot is only taken once when the magnifier is activated. In fact, I don't think we care about efficiency at all for this kind of little tool.
But thanks a lot for the link, that's super interesting, and they included a "ExcludeFromCapture" which would have been very convenient! I'll have a look how if I can integrate this into a Tauri backend!