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Subject: Re: [geometry] Buffer/Offsetting Polygon with holes
From: yohann.benedic_at_[hidden]
Date: 2014-05-21 09:39:25

>Unless you want to support a buffer with a negative distance....
You're right, but a slight modification of the algorithm gives you negative buffering. The Minkowski sum algorithm is first "thickening" every ring of the multipolygon by the size of the circle. It then computes the union of the thick rings with the original polygon to get the Minkowski sum result. That would emulate buffer with positive distance. Compute a difference with the original polygon instead of the union and the result emulates a buffer with a negative distance.

Note that I am not saying that this is the cleverest thing to do. It is my current workaround and again, this piece is not a bottleneck on my side and hence, the poor performance of that algorithm doesn't impact much on the overall performance.


Yohann Bénédic
Wireless Engineering and Propagation
Research Engineer
tel. +33 384 544 338


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