Since iOS 8, use the PhotoKit framework to access photos in albums:
PhotoKit | Apple Developer Documentation
I have an import for it, here:
https://github.com/DelphiWorlds/Kastri/blob/master/API/DW.iOSapi.Photos.pas
Which likely needs updating, because I think I imported it around iOS 9 era. This will not help you however, if you are saving photos as files somewhere. You can retrieve the filename from an asset in the gallery, bearing in mind can be traps in doing so:
https://medium.com/@slk11075/traps-for-phasset-how-to-get-filename-from-phasset-67d856e75c64