If Layer BoundingBoxes intersect, Use Intersection Center for all Layer Thumbnails

[fm3]

URL of deployed dev instance (used for testing):

• https://thumbnailstablecenter.webknossos.xyz

Steps to test:

• Set up a dataset with properties so that the layer bounding boxes are not equal
• Request thumbnails for these layers, i.e. http://localhost:9000/api/datasets/sample_organization/dsA/layers/segmentation/thumbnail, http://localhost:9000/api/datasets/sample_organization/dsA/layers/color/thumbnail
• The thumbnails should show the same region of the dataset

Issues:

• fixes Thumbnails for layers don’t seem to use the same position/zoom #6405

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• Ready for review

[jstriebel]

LGTM 👍

[philippotto]

👍

What happens if the intersection is empty? Rather unlikely, but a reasonable default would be cool.

[fm3]

I wanted to return None if there is no intersection, because otherwise the returned empty bbox carries an arbitrary topleft, which seemed weird. Also, the center of a zero-volume box may still be defined, depending on how you understand it. And my code needs to find out if there is no intersection, because then it passes None to the datastore as center, which will then again use each layer’s individual bounding box, to answer @philippotto’s question as well