Not getting the rectangle center when passing a rectangle as polygon

[SBRK]

I'm using this to add labels to random shape polygons, mainly because I can sometimes get "L" shaped polygons and using the barycenter would give me points outside of the polygon. It works pretty good on those cases, but on very simple cases, I'm getting bad results.

On rectangular shapes, I most of the time get a point close to one of the 4 sides. I would expect a point in the dead center in those cases.

[mourner]

Let's close this as a duplicate of #33