XCode Save Image with Overlay

I have a published APP in the iTunes store. I want to upgrade it by adding more features. Currently this app takes a picture and then saves that picture to the camera roll. Then the user selects that picture or any other picture from the camera roll and uses it in the app. The APP, (when positive results are achieved) then overlays another image on top of the image which was selected by the user. I need help saving that image combined with the overlay to the camera roll so that it can be shared to FB or email or what ever. PLEASE UNDERSTAND: this app is completed already. I want to create this as an update. I DO NOT need you to write a new app for me. NOTE: This was my first ever app in the app store so the code is a bit sloppy, but it functions. Upon award you shall get the raw code to help make adjustments. Please only experienced xcode and IOS developers only. It may help for you to provide proof of other APP store accepted items.