| Home | Libraries | People | FAQ | More

##### closest_points

Compute the closest points between two geometries.

###### Description

The free function closest_points calculates the closest points between two geometries. It uses the default strategy, based on the coordinate system of the geometry.

###### Synopsis

    template<typename Geometry1, typename Geometry2, typename Segment>
    void closest_points(Geometry1 const & geometry1, Geometry2 const & geometry2, Segment & shortest_seg)

###### Parameters

Type | Concept | Name | Description
--- | --- | --- | ---
Geometry1 const & | Any type fulfilling a Geometry Concept | geometry1 | A model of the specified concept
Geometry2 const & | Any type fulfilling a Geometry Concept | geometry2 | A model of the specified concept
Segment & | Any type fulfilling a Segment Concept | shortest_seg | Output segment containing the closest points

###### Header

Either

`#include <boost/geometry.hpp>`

Or

`#include <boost/geometry/algorithms/closest_points.hpp>`

###### Example

Shows calculation of the two closest points between two geometries

    #include <iostream>

    #include <boost/geometry.hpp>
    #include <boost/geometry/geometries/linestring.hpp>
    #include <boost/geometry/geometries/point_xy.hpp>
    #include <boost/geometry/geometries/polygon.hpp>
    #include <boost/geometry/geometries/multi_point.hpp>

    int main()
    {
        typedef boost::geometry::model::d2::point_xy<double> point_type;
        typedef boost::geometry::model::polygon<point_type> polygon_type;
        typedef boost::geometry::model::linestring<point_type> linestring_type;
        typedef boost::geometry::model::multi_point<point_type> multi_point_type;

        point_type p(4.3,1.9);
        point_type p0(0,0);
        polygon_type poly;
        linestring_type line;
        multi_point_type mp;

        boost::geometry::read_wkt(
            "POLYGON((2 1.3,2.4 1.7,2.8 1.8,3.4 1.2,3.7 1.6,3.4 2,4.1 3,5.3 2.6,5.4 1.2,4.9 0.8,2.9 0.7,2 1.3)"
            "(4.0 2.0, 4.2 1.4, 4.8 1.9, 4.4 2.2, 4.0 2.0))", poly);
        line.push_back(point_type(5,0));
        line.push_back(point_type(2,0));
        mp.push_back(point_type(2,0.5));
        mp.push_back(point_type(2,3));

        boost::geometry::model::segment<point_type> sout1,sout2,sout3;

        boost::geometry::closest_points(p, poly, sout1);
        std::cout << "Point-Poly: " << boost::geometry::wkt(sout1) << std::endl;

        boost::geometry::closest_points(poly, line, sout2);
        std::cout << "Poly-Line: " << boost::geometry::wkt(sout2) << std::endl;

        boost::geometry::closest_points(poly, mp, sout3);
        std::cout << "Poly-MultiPoint: " << boost::geometry::wkt(sout3) << std::endl;

        return 0;
    }

Output:

    Point-Poly: LINESTRING(4.3 1.9,4.2 2.1)
    Poly-Line: LINESTRING(2.9 0.7,2.9 0)
    Poly-MultiPoint: LINESTRING(2.36923 1.05385,2 0.5)

###### See also

- distance