Dear Andreas, On 12/06/2015 09:49 πμ, Andreas Wimmer wrote:

Dear Boost Geometry Contributors,

could you please re-post to the Boost.Geometry dedicated mailing list: geometry@lists.boost.org Thanks. - m.

I am testing the boost::geometry::dissolve function upon some invalid polygons that are produced by a certain in-house segmentation alg. The fact that the algorithm is producing possibly invalid polygons cannot be changed easily so I thought I will fix them afterwards using dissolve from “geometry/extensions/algorithms/dissolve.hpp” for the latest boost 1.58 version. Unfortunately I stumbled over the following polygons for which dissolve produces wrong results.

The following code illustrates the result

using namespace boost::geometry; using namespace boost::geometry::model; using namespace boost::geometry::model::d2;

int main(int argc, _TCHAR* argv[]) { polygon< point_xy<float> > Poly; read_wkt("POLYGON((10 10, 10 20, 20 20, 15 12, 15 18, 20 10, 10 10))", Poly);

multi_polygon< polygon< point_xy< float > > > Dissolved; boost::geometry::dissolve(Poly, Dissolved); }

Which results in a polygon including the small intersection part which should be excluded from the polygon

And even more problematic the following example (same polygon with and additional self-touching outer ring) results in missing the entire main part of the polygon

int main(int argc, _TCHAR* argv[]) { polygon< point_xy<float> > Poly; read_wkt("POLYGON((10 10, 10 20, 20 20, 20 25, 22 25, 20 20, 15 12, 15 18, 20 10, 10 10))", Poly);

multi_polygon< polygon< point_xy< float > > > Dissolved; boost::geometry::dissolve(Poly, Dissolved); }

I hope somebody can show me what I did wrong or what I can to too work around this problem.

Best regards,

Andreas Wimmer

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