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##### envelope

Calculates the envelope of a geometry.

###### Description

The free function envelope calculates the envelope (also known as axis aligned bounding box, aabb, or minimum bounding rectangle, mbr) of a geometry.

###### Synopsis

    template<typename Geometry, typename Box>
    void envelope(Geometry const & geometry, Box & mbr)

###### Parameters

Type | Concept | Name | Description
--- | --- | --- | ---
Geometry const & | Any type fulfilling a Geometry Concept | geometry | A model of the specified concept
Box & | Any type fulfilling a Box Concept | mbr | A model of the specified Box Concept which is set to the envelope

###### Header

Either

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

Or

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

###### Conformance

The function envelope implements function Envelope from the OGC Simple Feature Specification.

###### Example

Shows how to calculate the bounding box of a polygon

    #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/io/wkt/wkt.hpp>

    int main()
    {
        typedef boost::geometry::model::d2::point_xy<double> point;

        boost::geometry::model::polygon<point> polygon;

        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))", polygon);

        boost::geometry::model::box<point> box;
        boost::geometry::envelope(polygon, box);

        std::cout << "envelope:" << boost::geometry::dsv(box) << std::endl;

        return 0;
    }

Output:

    envelope:((2, 0.7), (5.4, 3))