A rectangular region can be selected by clicking and dragging with the left mouse button.
Dragging on the middle of one of the four borders of the selected area (when the cursor is showing an ``edge'' symbol) resizes the selected area. Dragging on the corner (a ``fleur'' symbol) grabs the selected area and copies it to another location.
The size of the selected area can also be changed in one-pixel increments with Shift+Numeric keypad keys. The mouse cursor must be somewhere in the image area for the keystrokes to be received. This permits precise positioning of the selected area.
A rectangular region can also be selected by selecting two image points. Press the Shift key and left-click to select the first point. Release the mouse and shift-click again to select a second point. The difference between this method and the click-and-drag method is that the points are fixed on the image instead of the screen. This means you can move the image around with the mouse or arrow keys before selecting the second point. This can be useful in selecting areas larger than the screen, which would be impossible to select with click-and-drag.