function:
Crop a picture into a circle using your finger.

Instructions:
1. Click "Crop Image" on the menu.
2. Click "Load Image" button (read / write permission may be required).
3. Select a picture to crop in a circle shape.
4. Click the "Crop Image" button.
5a. Use one finger to move the circle area in the preview.
5b. Use two fingers to stretch circles to different sizes in the preview.
6. Click "Save Image" and wait for the process to complete.
7. When finished, you will find the circle image in the gallery.