Maybe Shutter, it has a few GNOME dependencies however (some are optional).
> Shutter is a feature-rich screenshot program. You can take a screenshot of a specific area, window, your whole screen, or even of a website – apply different effects to it, draw on it to highlight points, and then upload to an image hosting site, all within one window. Shutter is free, open-source, and licensed under GPL v3.
Or you could write a script that asks for confirmation and bind this to the `PrtSc` key.