A thought just occurred to me. Wouldn’t it be useful to have the border scanned as well? My understanding is that it is printed using the photographic process, so it is the 3 color black and should faded in the same way. So couldn’t it be used to better predict the original unfaded colors? Just a thought. I like the way your algorithm works. It makes some very nice images.
Yes, that would certainly be very helpful, if it is available.