# Boost C++ Libraries

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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

Either

#include <boost/geometry/geometry.hpp>

Or

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

###### 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/domains/gis/io/wkt/wkt.hpp>

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

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

"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))

 Copyright © 2011 Barend Gehrels, Bruno Lalande, Mateusz Loskot Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)