ceph/src/boost/libs/geometry/doc/src/examples/algorithms/area.cpp

   1 // Boost.Geometry (aka GGL, Generic Geometry Library)
   2 // QuickBook Example
   3
   4 // Copyright (c) 2011-2012 Barend Gehrels, Amsterdam, the Netherlands.
   5
   6 // Use, modification and distribution is subject to the Boost Software License,
   7 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   8 // http://www.boost.org/LICENSE_1_0.txt)
   9
  10 //[area
  11 //` Calculate the area of a polygon
  12
  13 #include <iostream>
  14
  15 #include <boost/geometry.hpp>
  16 #include <boost/geometry/geometries/point_xy.hpp>
  17 #include <boost/geometry/geometries/polygon.hpp>
  18
  19 namespace bg = boost::geometry; /*< Convenient namespace alias >*/
  20
  21 int main()
  22 {
  23     // Calculate the area of a cartesian polygon
  24     bg::model::polygon<bg::model::d2::point_xy<double> > poly;
  25     bg::read_wkt("POLYGON((0 0,0 7,4 2,2 0,0 0))", poly);
  26     double area = bg::area(poly);
  27     std::cout << "Area: " << area << std::endl;
  28
  29     // Calculate the area of a spherical equatorial polygon
  30     bg::model::polygon<bg::model::point<float, 2, bg::cs::spherical_equatorial<bg::degree> > > sph_poly;
  31     bg::read_wkt("POLYGON((0 0,0 45,45 0,0 0))", sph_poly);
  32     area = bg::area(sph_poly);
  33     std::cout << "Area: " << area << std::endl;
  34
  35     return 0;
  36 }
  37
  38 //]
  39
  40
  41 //[area_output
  42 /*`
  43 Output:
  44 [pre
  45 Area: 16
  46 Area: 0.339837
  47 ]
  48 */
  49 //]