Download images in file system

I need to save bunch of images in device file system to view them offline,
but images should only accessible from the app .So if anyone try to view them from file system it should not accessible.How to do that i dont have any idea for that ?

This page may help you:

I think you must save your images in the “applicationDirectory”.

The one that’s described as “read-only”? Not going to happen.

Yes, you’re right. My fault.