Link to start page in IIIF scans

[craigsapp]

On work pages, links to scans usually do not always point to the starting page of the transcription. For Humdrum files, this information is stored in the first IIIF tandem interpretation. Extract from this interpretation and add the starting page to the URL-scan column on the metadata spreadsheet.

16xx:984 is an example case where there are multiple links for the parts of a complete score.

Probably only update Polona and NIFC image links (do other repository scan webpages if they allow access at the page (image) level.

[craigsapp]

Marenzio is another exaple:

https://polishscores.org/?id=15xx:989

The link:

Goes to the URL:

https://polish.musicsources.pl/en/lokalizacje/galeria/klocki-introligatorskie/655/1#nomenu

Which is the first page of a 732 scans entry.

There are two things, one is to give the first page for the link. But also this score needs separate links to separate scans in the source document. This part-level information is extractable from the Humdrum data, such as in this case:

*xywh-pl-gd--ee1638-8o--0189:4666,1770,3361,676
*xywh-pl-gd--ee1638-8o--0341:4679,1783,3328,659
*xywh-pl-gd--ee1638-8o--0493:4570,2341,3448,647
*xywh-pl-gd--ee1638-8o--0645:4610,1765,3358,667

the basso part starts at scan 189 (1-indexed), the tenore at page 341, the alto at page 493 and the canto at page 645.

[craigsapp]

This of course can only be done with the bounding box data is encoded in the Humdrum scores (so the rest of the bounding box info should be added to the Humdrum scores :-)