Snapchat Keeper by Noah Moroze (This app requires root to function)
Shell class borrowed from Adam Outler (see class for licensing info)
You are free to use this code in a non-commercial context and with attribution to the creator
This app allows you to permanently keep Snapchat images. To use, simply ensure that snaps have been loaded but not opened (it will say 'press and hold to view' below the snap). Open this app and press the button. Your unopened snaps will automatically be stored as standard jpeg files under Kept_Snaps in the Pictures folder.
As snaps are expected to be erased, please do not violate someone's privacy and warn them ahead of time if you are storing the image they sent you.