Combine Rectangular Selections in GIMP

Combining multiple intersecting rectangular selections in GIMP allows you to create complex selection shapes quickly without manual drawing. By using the Rectangle Select Tool alongside keyboard modifier keys such as Shift and Ctrl, you can seamlessly add intersecting areas together to form a unified selection or isolate only the overlapping regions where selections meet.

1. Activate the Rectangle Select Tool

Press the R key on your keyboard or select the Rectangle Select Tool from the main Toolbox. Create your initial rectangular selection by clicking and dragging on the canvas.

2. Add Selections Together (Union)

To combine two or more intersecting rectangles into a single continuous shape:

  1. Ensure your first selection is active.
  2. Press and hold the Shift key. A small plus sign (+) will appear next to your mouse cursor, indicating the "Add to current selection" mode.
  3. While holding Shift, click and drag to draw your second intersecting rectangle.
  4. Release the mouse button first, then release the Shift key.

The two intersecting rectangles will merge into a single, combined outline. Repeat this process with additional rectangles to expand the selection further.

3. Keep Only the Overlapping Area (Intersection)

If your goal is to extract strictly the area where two rectangular selections overlap:

  1. Draw your primary rectangle selection.
  2. Press and hold both Ctrl and Shift simultaneously. An intersection symbol will appear beside the mouse cursor.
  3. Click and drag the second rectangle across the first.
  4. Release the mouse button, then release the keys.

All areas outside the overlapping boundary will be discarded, leaving only the exact intersecting region selected.

Tips for Using Modifier Keys

  • Order of actions matters: Always press and hold the modifier key before clicking to begin the new selection. If you click first and then press the key, GIMP will interpret the action as moving the existing selection instead of modifying it.
  • Tool Options Panel: If you prefer not to hold keyboard keys, you can manually toggle these behaviors in the Tool Options panel under the Mode setting by choosing either the Add to current selection icon or the Intersect with current selection icon.