Function:
Crop photo into circular shape by fingers.

Instruction:
1. Click "Crop Circle" at Menu
2. Click "Load Photo" Button (Read/Write Permission may be required)
3. Choose a photo to be cropped in circular shape.
4. Click "Crop Circle" Button
5a. Use single finger to move the circular region in preview.
5b. Use two fingers to stretch the circle to different size in preview.
6. Click "Save Photo" and wait for processing and completion.
7. When completed, you can find a circular photo in the gallery.