...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Converts one geometry to another geometry.
The convert algorithm converts one geometry, e.g. a BOX, to another geometry, e.g. a RING. This only works if it is possible and applicable. If the pointorder is different, or the closure is different between two geometry types, it will be converted correctly by explicitly reversing the points or closing or opening the polygon rings.
template<typename Geometry1, typename Geometry2> void convert(Geometry1 const & geometry1, Geometry2 & geometry2)
Type 
Concept 
Name 
Description 

Geometry1 const & 
Any type fulfilling a Geometry Concept 
geometry1 
A model of the specified concept (source) 
Geometry2 & 
Any type fulfilling a Geometry Concept 
geometry2 
A model of the specified concept (target) 
Either
#include <boost/geometry.hpp>
Or
#include <boost/geometry/algorithms/convert.hpp>
The function convert is not defined by OGC.
Point 
Segment 
Box 
Linestring 
Ring 
Polygon 
MultiPoint 
MultiLinestring 
MultiPolygon 


Point 









Segment 









Box 









Linestring 









Ring 









Polygon 









MultiPoint 









MultiLinestring 









MultiPolygon 









Note  

In this status matrix above: columns are source types and rows are target types. So a box can be converted to a ring, polygon or multipolygon, but not vice versa. 
Linear
Shows how to convert a geometry into another geometry
#include <iostream> #include <boost/geometry.hpp> #include <boost/geometry/geometries/box.hpp> #include <boost/geometry/geometries/point_xy.hpp> #include <boost/geometry/geometries/polygon.hpp> #include <boost/geometry/geometries/adapted/boost_tuple.hpp> BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian) int main() { typedef boost::geometry::model::d2::point_xy<double> point; typedef boost::geometry::model::box<point> box; typedef boost::geometry::model::polygon<point> polygon; point p1(1, 1); box bx = boost::geometry::make<box>(1, 1, 2, 2); // Assign a box to a polygon (conversion box>poly) polygon poly; boost::geometry::convert(bx, poly); // Convert a point to another point type (conversion of pointtype) boost::tuple<double, double> p2; boost::geometry::convert(p1, p2); // source > target using boost::geometry::dsv; std::cout << "box: " << dsv(bx) << std::endl << "polygon: " << dsv(poly) << std::endl << "point: " << dsv(p1) << std::endl << "point tuples: " << dsv(p2) << std::endl ; return 0; }
Output:
box: ((1, 1), (2, 2)) polygon: (((1, 1), (1, 2), (2, 2), (2, 1), (1, 1))) point: (1, 1) point tuples: (1, 1)
Note  

convert is modelled as source > target (where assign is modelled as target := source) 