I get: `viewof img = Error: File not found: petits_objets.jpg`

thanks I was not looking at the published version ;)

The selection zone seems to be blurred. Try with a map, for example: the labels are clear in the background image, but not in the selection zone. Maybe it's related to devicePixelRatio (=2 on my screen)

When included inside a "details" HTML tag, the sub-image is shifted. See https://observablehq.com/d/fb601eb60f7bcb5f