Feature request: Allow radii to be extracted from fills in a more convenient way

[tferr]

Discussed here:
https://forum.image.sc/t/snt-3d-reconstruction-to-2d-segmentation-masks/86519#2

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/snt-3d-reconstruction-to-2d-segmentation-masks/86519/2