Behaviour of non-upscaling, confined image in IIIF v3

[tomcrane]

Consider a source image with pixel dimensions 300,300 and a IIIF v3 image service.

If the request is /full/^!400,400/.. then the server can only return an image if the max_scale config setting allows it. If set to 1.0 it will not allow this request.

400 Bad Request
Requests for scales in excess of 100% are not allowed.

If the request is /full/!400,400/.. (no upscaling instruction, just a confinement instruction), and max_scale is (say) 1.0, Cantaloupe returns:

400 Bad Request
Requests for scales in excess of 100% must prefix the scale path component with a ^ character.

However, I think Cantaloupe could return the image at its natural size (300,300) for this request,

The spec says:

!w,h
The extracted region is scaled so that the width and height of the returned image are not greater than w and h, while maintaining the aspect ratio. The returned image must be as large as possible but not larger than the extracted region, w or h, or server-imposed limits.

The spec allows some leeway for the server here. An example scenario is a page full of thumbnails confined to a particular size, where interrogating the info.json of each image service in advance would be too much for the client.