From The Document Foundation Wiki
How do I crop an image?
With the image already inserted in Draw:
- Click the image to select it (just once). Just below the command bar, the Image Toolbar will appear;
- In the toolbar, click the Crop button;
- The handles of the image are now thicker. Click and drag to adjust the cropped area;
- Click outside the image to deselect or use the Escape button on your keyboard.