Erase part of a picture

Play

1. Select the picture, then tap the eraser in the stage's corner (or press E).
2. Set its Size in the bar along the top of the stage.
3. Drag over what you want to remove.
4. Tap Done.

The cut line follows what's left. Each stroke is one step of Undo. The eraser puts itself away as soon as you do something else (add text or a picture, open another panel, change an option), so you're back to selecting and moving.