pct regions don't always behave correctly

[kamholz]

Image regions retrieved using pct: (https://iiif.io/api/image/2.1/#region) don't always return the right results. Here is a demonstration for an image whose full dimensions are 5616x3744. When requesting a region that is 50% of the original width and height, starting from (0%, 0%):

https://iiif.archivelab.org/iiif/tutur-smara-bhuwana%242/pct:0,0,50,50/full/0/default.jpg

the result is 2808x1872, as expected. However, when requesting a region starting from (10%, 10%):

https://iiif.archivelab.org/iiif/tutur-smara-bhuwana%242/pct:10,10,50,50/full/0/default.jpg

the result is 2620x1872, i.e. it is not wide enough. Per the spec, the different origin should not make a difference. And the requested region is entirely contained within the original image, so it should not be cropped.

Finally, some valid requests return 404, such as this one:

https://iiif.archivelab.org/iiif/tutur-smara-bhuwana%242/pct:78.22,33.42,9.94,2.09/full/0/default.jpg

I haven't investigated in more detail than this. Regions specified in pixels (without pct:) seem to work fine.