Misaligned strip of tiles(?) in UV V4 on default zoom load

[WilsonAndrewWilson]

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 universalviewer@[email protected]

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• [x] bug report
• [ ] feature request => please use the user stories repo
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Current behavior: On certain images, the inner most strip is not displaying correctly in either paged or individual views in UV V4. UV V3 is showing them fine. The "out of alignment" issue goes away after a couple of zooms.

(Note from @edsilv : could be due to latest version of OSD in V4, it appears to not be loading the correct tiles when fully zoomed out).

Expected behavior: the inner strip is aligned.

Steps to reproduce: Go to https://uv-v4.netlify.app/#?c=&m=&cv=15&manifest=https%3A%2F%2Fcollections.st-andrews.ac.uk%2F774289%2Fmanifest&s=&xywh=-173%2C-725%2C9124%2C7837 and there should be a misaligned strip on the left page, down the inside. Switching to individual viewing does not make this go away. Only zooming fixes this.

Compare to : https://uv-v3.netlify.app/#?c=&m=&cv=15&manifest=https%3A%2F%2Fcollections.st-andrews.ac.uk%2F774289%2Fmanifest&s=&xywh=-174%2C-926%2C9124%2C8237

Related code:

// insert any relevant code here

Other information:

[edsilv]

Can this be reproduced in other Openseadragon based viewers? Seems like it might be a problem with your image pyramids?

[edsilv]

Am seeing a slight aberration on v3 too - although not as pronounced. I think we could try to reproduce this in a separate test harness in glitch or similar to see if it's just related to the version of OSD and whether that version of OSD has the same issue for images from a different source. The problem strip: https://collections.st-andrews.ac.uk/iiif/2/434173~434173/4096,0,155,4096/20,/0/default.jpg

[irv]

I think there's a rounding error in the image server

Using Tom's tile exploder: http://tomcrane.github.io/presentations/tile-exploder.html with the image: https://collections.st-andrews.ac.uk/iiif/2/434173~434173/info.json

You can see immediately at scale factor 8:

The tile request https://collections.st-andrews.ac.uk/iiif/2/434173~434173/4096,0,155,4096/20,/0/default.jpg is expected to be 20,512 to match the 512,512 of https://collections.st-andrews.ac.uk/iiif/2/434173~434173/0,0,4096,4096/512,/0/default.jpg

requesting that tile at full comes back at 155,4096 which when scaled down to 20 height maintaining aspect ratio does I think scale to 20,512

and I think you can confirm that by comparing the dimensions of https://collections.st-andrews.ac.uk/iiif/2/434173~434173/4096,0,155,4096/!20,512/0/default.jpg and https://collections.st-andrews.ac.uk/iiif/2/434173~434173/4096,0,155,4096/20,512/0/default.jpg

[stephenwf]

I think that's correct @irv. However trying in an independent tile renderer it is possible for a viewer to work around it. Maybe something OSD could look to fix

[LlGC-szw]

All issues will be triaged for further investigation or closure by the 28 September 2023. If your issue is still relevant and would like for it be investigated further please comment by 14 September 2023.