If someone is interested, Alex Brollo is digging into the djvu layer issue, we have a Dropbox folder with all the files. If you are interested in working on that, please drop me a mail.
What we can show you right now is this: https://www.dropbox.com/s/lu6re2a02xp0nyc/Dialogo%20della%20salute%20djvu%20...
As you can see, the text is not mapped again into the djvu, but it is "stored" all togheter in a region of the djvu page (in this case, left angle below). It is very difficult to re-map the text, for example because when we use the tag <ref> for footnotes we destroy the pattern :-(
The cool thing is that the text inside is already formatted in wikitext! https://www.dropbox.com/s/s2c0op5e9jeu47o/Dialogo%20della%20salute%20WS%20ss... Alex assures me this is easy and just uses few scripts from djvulibre (which is already installed in toolserver). The same could be made uploading wiki-rendered HTML into text layer.
This could be very interesting for other websites: they could just copy-and-paste the HTML file, or extract it with a simple python script calling for djvuLibre routines, and then use the Commons file as a benchmark. We could, maybe, give back some of our books to the Gutenberg project. Or, maybe, give it back to GLAMs.
What do you think?
Aubrey and Alex