How to export edited pictures from 'Photos" app with Applescript while preserving the image metadata?

I have written long ago an Applescript script that exports pictures selected in Apple Photos app with various basic options, such as adding borders, adjusting size, tuning for Web publishing, etc, and the addition of metadata copyright info using an exiftool command thru a shell script. But I cannot figure how to preserve the original files metadata in the exported images, and this turns out to become a critical need now in my current activities. I am considering locating the original file in the "Masters" Photo Library folder, extracting and saving the metadata with an exiftool command, and applying the same metadata to the exported files, but the simple task of obtaining the POSIX path of the original file proves to be challenging (I am 72 years old) and the other tasks challenging as well. Anyone here with better ideas ?