[geos-devel] union to save a holes

[Sandro Santilli]

On Tue, Feb 28, 2017 at 02:46:47PM +0300, Gorbachev Ivan wrote:
> Hello!
> 
> I need to union a set of the polygons. But I need to save an all holes in
> the union. CascadePolygonUnion remove all holes in the result. How to do
> that ?

Holes should only be removed if there's a polygon in the input set
that covers those holes.

If you want to be sure all holes are kept compute the difference
between the result of the union of the polygons shells and the
union of the polygons holes.

--strk;