Add Maximum Inscribed Circle

[PieceMaker]

A Voronoi-based maximum inscribed circle algorithm based on the JavaScript library max-inscribed-circle.

OSGeo ticket https://trac.osgeo.org/geos/ticket/1028.

[nyalldawson]

Did you see #310 ?

[PieceMaker]

Wow, I did not see that. Beat me by a few days...

[dr-jts]

Also see this JTS blog post for more background.

My guess is that the iterative approach in #310 will be faster than the densified Voronoi approach. Would be interesting if you can compare them.

Also note that I plan to add a "viewport constraint" as well, to be able to find the visual centre of. a polygon which is only partially visible in a rectangular viewport.

And finally, others have experimented with this for label placement, and have actually decided that in itself MIC is not ideal for labelling. See some discussion in the Mapnik project for instance [1][2].

[1] mapnik/mapnik#3780
[2] mapnik/mapnik#3811

[dr-jts]

This enhancement to weight using centroid might also be worthwhile for labelling purposes:

Of course this is no longer the MIC then.

[PieceMaker]

@dr-jts Thank you very much for the links. That info is very insightful. I'll see if I can write a comparison once the iterative method is merged in.

I will go ahead and close this PR.