Quick screen capture application
Solution 1:
Gnome already does this.
- Shift + PrtSc allows you to draw the rectangle to capture.
- Ctrl + PrtSc captures the active window on the screen.
- PrtSc captures the entire screen.
It saves to your Pictures directory. You can change the save directory using dconf-editor.
No dialog, no GUI. Just a flash to provide you feedback that the image was captured.