Retrieve full-size images from IIIF servers

[Peter Robinson]

Folks

For various reasons (which might be the subject of a separate post) I would like retrieve full size images from IIIF servers. So far as I can see, this is a fairly straightforward process, at least in theory. Presume that the manifest of the image you are looking for is at address 

https://cdm16003.contentdm.oclc.org/digital/iiif/p15150coll7/2448/info.json

(folio 41v of the Ellesmere manuscript of the Canterbury Tales, in the Huntington library)

The full image of this page is at

https://cdm16003.contentdm.oclc.org/digital/iiif/p15150coll7/2448/full/full/0/default.jpg

This brings us back the full 2416x3000 pixel image. Nice!

However, some libraries which will remain nameless do NOT return the full-size image. Instead, the image at /full/full/0/default.jgp is at a much lower resolution. The IIIF viewer is able to zoom in on the image because it has access to the tiles made from the original image. But there does not seem to be any way of bringing. back the full size image from the manifest alone.

Some questions:

1. Is this behaviour of placing a lower resolution image at /fullfull/0/default.jpg in line with IIIF protocols?

2. Have I missed something? is there another address I should be trying? (full/max/0/default.jpg returns the same reduced quality image)

Another possibility is to rebuild the full-size originals from the tile sources. I'd rather avoid this, of course.

Advice please.

Peter