id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
9206,intersection of non-closed polygons returns closed polygon,Volker Schöch <volker@…>,Barend Gehrels,"The output multi-polygon from boost::geometry::intersection should have the same orientation, closed-ness and underlying scalar data type, as the input (multi-)polygons. My polygon type is '''oriented counter-clockwise''' and '''not closed''', my point type is based on '''int'''. Please find below some code that results in a closed polygon.

''Note: The sym_difference and difference algorithms have the same problem which I filed as separate tickets #8375, #8376.''

This is the data used as input to intersection:

{{{
_TPolygon<int> const polygon =
	_TPolygon<int>(""MULTIPOLYGON(((1374 1092,1734 1092,3174 2526,3174 2886,1374 2886)))"")
	& _TPolygon<int>(""POLYGON((2817 2449,2817 2603,3134 2603,3134 2449,2817 2449))"");
}}}

This is the resulting multi-polygon, with the polygon being closed:

{{{
MULTIPOLYGON(((3134 2486,3134 2603,2817 2603,2817 2449,3096 2449,3134 2486)))
}}}

This is my code that wraps boost::geometry to implement the operator used above:

{{{
template<typename T>
template<typename Geometry>
_TPolygon< T > _TPolygon< T >::operator&(Geometry const& geometry) const
{
	_TPolygon< T > polygonOut;
	boost::geometry::intersection(*this, geometry, polygonOut);

	// should not be necessary
	//boost::geometry::correct( polygonOut );

	return polygonOut;
}
}}}
",Bugs,closed,To Be Determined,geometry,Boost 1.55.0,Problem,invalid,"intersection, multi-polygon, polygon, closed, open, correct",mkaravel