Add support for IIIF Image API 3.0 beta

[lutzhelm]

Solves #1734.

Of the list in #1734 (comment) all items are implemented, except

• "The full region is now just max" - this probably refers to the size, not the region. Full / max size has already been addressed with the max size parameter.
• Splitting the code in several classes for the different API versions

[eroux]

Thanks! I haven't looked closely at the rest, but the part that modifies the getTileUrl looks good to me

[iangilman]

Fantastic! Thank you for doing this. It all looks reasonable to me, but I'm not terribly familiar with IIIF, so I value others' input. Thank you for including the test module!

[iangilman]

It would probably be good to do a $.console.error here. Also, perhaps we should set some sort of default version? Either that or properly error out.

[lutzhelm]

I added an error message.
I'm not sure I'd be able to suggest a default version. Currently version 2.x is probably the most common version, but I don't know in what situation an image service would fail to provide a correct context URI.
Any suggestion are welcome.

[iangilman]

Cool… Just having an error is probably fine then.

[iangilman]

@eroux Thank you for taking a look!

@azaroth42 Can you take a look as well?

@lutzhelm What are your thoughts on the remaining bits you haven't done? Would you like to get them into this patch as well, or do you think they aren't necessary?

[lutzhelm]

@lutzhelm What are your thoughts on the remaining bits you haven't done? Would you like to get them into this patch as well, or do you think they aren't necessary?

• I'd refrain from splitting IIIFTileSource into separate classes for each version with a common ancestor for now. The code is currently more, but I'm not sure the parts that are not common between versions are that easy to isolate; common parts, on the other hand, should not be copied. Maybe anyone has a suggestion on that.
• I don't know what @azaroth42 meant by "The full region is now just max". The full size (not region) parameter has been replaced with max for version 3. max was already part of version 2, but it wasn't required to be supported by images services. OpenSeadragon did however already use max instead of full. I found another thing about the size parameter that I mentioned in my comment under the original issue, but that is another issue which I would'nt address in this pull request:

I do (again) wonder if the size parameter should be given as full instead of w, (version 2) / max instead of w,h (version 3) if the requested size has the same resolution as the full image. This would be especially important for level 0 compliant image services.

[azaroth42]

Sorry, I mispoke in haste! the full size parameter is now just max, as @lutzhelm says. full is removed, as it's meaningless when there's also max.

[iangilman]

The new changes look good. It seems this is ready to merge… Would you agree, @lutzhelm, @eroux, @azaroth42? If so, can you take it out of draft, @lutzhelm?

[eroux]

ok for me yes!

[azaroth42]

LGTM! :)

[lutzhelm]

There we go.

[iangilman]

Awesome... thank you for doing this!