3
I had a look at my database on this and it would appear that the database only contains data about the image, and not the image itself.
It should therefore not be too difficult for a PHP script to be written that read each file in a directory, gets the image dimensions and filesize attributes and writes that to the database. It is certainly within the realms of doable.
The trickiest part would be matching the file with the right one in the database, but if the filenames are unchanged then this would not be too hard.