evaluate IIIF image options

[evanwill]

CONTENTdm implementation of IIIF has some limitations.

currently:

• image includes use pct: with % set in the theme.yml, e.g. large pct:70. this works consistently with most collections, unless the images in CDM are abnormally large or small. However, using % is a bit random since you don't know the starting size. Secondly, CDM does not seem to allow less than 10%.
• carousel include uses just the height, ,h based on the height of the carousel. This ensures the image makes sense in that location, but can end up with odd sizes for images with extreme ratios, large landscape or large vertical images.

going forward:

• best option would be !w,h which should give something scaled to best fit inside those dimensions, but CDM is just returning max instead. so unfortunately this doesn't work.
• do we want to switch from pct: to height or width?

[evanwill]

@owikle @dcnb we should think about this, and then document how the API works and what to consider if it isn't working for a specific collection.

I would also like to figure out a way to create a recipe for the API call for use in JS includes. And maybe just restructuring the image includes in general to make it easier to swap out APIs.

I added a bit more info to the docs:

https://github.com/CollectionBuilder/collectionbuilder-contentdm/blob/master/docs/contentdm-api.md

[evanwill]

CDM IIIF api returns nothing if image is smaller than the requested pixel dimensions.
e.g.

• this image max is 687x464, https://digital.lib.uidaho.edu/digital/iiif/psychiana/722/full/max/0/default.jpg
• if you request 700pixel image, it breaks, https://digital.lib.uidaho.edu/digital/iiif/psychiana/722/full/700,/0/default.jpg
• https://digital.lib.uidaho.edu/digital/iiif/psychiana/722/full/,700/0/default.jpg
• https://digital.lib.uidaho.edu/digital/iiif/psychiana/722/full/700,700/0/default.jpg