I thought the conclusion was that Ancestry assigned the JPG file extension to GIF and TIFF files in some of its databases over some period of time. If that is correct, it is not RootsMagic's handling of the GEDCOM from FTM that is at fault. Nor does it seem to be a widely reported issue. It seems moot that RootsMagic should undertake to detect these mistyped files and take any corrective action.
Instead of fixing your 720 defective filenames one at a time, perhaps a procedure along these lines would have speeded things up:
- Run GraphicMagick or equivalent to detect the mismatched extensions.
- Use the results from that to build in a spreadsheet a series of Windows commands to make copies of the files with the correct extension.
- Execute the command line file from 2. Now we have the files correctly named but not linked to RootsMagic.
- Use the GraphicMagick results to build in the spreadsheet a series of SQLite commands to UPDATE the MultiMediaTable columns that contain the path and filename of these mismatched files so that they will point to the corrected files.
- Execute the batch of SQLite commands in a SQLite manager.
That should result in RootsMagic being happy with the corrected files.
An alternative would be to replace steps 4 and 5 with operations on the GEDCOM file using a text editor having a scripting language such as Notepad++ and then import the GEDCOM into a new database.
Admittedly, both may be daunting procedures for most people so, if it were a common problem, it could be in RootsMagic's interest to build in an automatic solution.