Click-and-drag selection
Why do I have to type the hotkey, then drag, then type the hotkey again? This feels unnecessarily complicated. I suggest changing it to hotkey + click-and-drag. Or maybe add an option to choose the behavior?
The reason is that dpScreenOCR doesn't block neither keyboard nor mouse when the selection is active. This is by design.
The click-and-drag behavior requires "freezing" the screen image (to show it in a fullscreen overlay window) and capturing all keyboard and mouse events. I understand that this is how most screenshot programs work, but this doesn't work well with fullscreen apps: when you grab the mouse or show another fullscreen window (i.e., the mentioned overlay), most fullscreen apps will minimize their windows.