Detection of too similar annotations for non bounding boxes does not work well enough

[johagge]

Is your feature request related to a problem? Please describe.

When using bounding boxes to annotate something and a too similar annotation already exists, the user is informed and the annotation is discarded.
If the user does the same with two polygons instead of a bounding box, no warning is given and the annotation is added.

Describe the solution you'd like

I would expect the same behavior for bounding boxes and polygons (and other annotation types).

[timonegk]

This feature currently exists but it does not seem to work well enough for most labels because the new polygon points have to match the existing very closely. The current solution could be replaced by calculating the center point of the enclosing boundling box and looking for the distance to the center of the new annotation.