Description
This was originally raised with OpenSeaDragon in the following issue:
openseadragon/openseadragon#2321
Currently the IIIF specification states that the rounding method is implementation specific. This can cause problems particularly with a level0 image which has dimensions that don't divide by the scaleFactor into a whole number. Most implementations seems to have gone for ceil as this matched the method in OSD. When OSD changed to round it caused some of the size requests to be off by 1 pixel.
The OSD issue has been resolved by @ruven who has implemented an alternative algorithm looking at the sizes array. The sizes array is optional so if it isn't provided currently OSD will fall back to the ceil method.
I created this issue so that it can be tracked and discussed if anything needs to be done with the next IIIF version.