libs/geometry/doc/src/examples/algorithms/centroid.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 //[centroid
  11 //` Shows calculation of a centroid of a polygon
  12
  13 #include <iostream>
  14 #include <list>
  15
  16 #include <boost/geometry.hpp>
  17 #include <boost/geometry/geometries/point_xy.hpp>
  18 #include <boost/geometry/geometries/polygon.hpp>
  19 /*<-*/ #include "create_svg_two.hpp" /*->*/
  20
  21 int main()
  22 {
  23     typedef boost::geometry::model::d2::point_xy<double> point_type;
  24     typedef boost::geometry::model::polygon<point_type> polygon_type;
  25
  26     polygon_type poly;
  27     boost::geometry::read_wkt(
  28         "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)"
  29             "(4.0 2.0, 4.2 1.4, 4.8 1.9, 4.4 2.2, 4.0 2.0))", poly);
  30
  31     point_type p;
  32     boost::geometry::centroid(poly, p);
  33
  34     std::cout << "centroid: " << boost::geometry::dsv(p) << std::endl;
  35     /*<-*/ create_svg("centroid.svg", poly, p); /*->*/
  36     return 0;
  37 }
  38
  39 //]
  40
  41 //[centroid_output
  42 /*`
  43 Output:
  44 [pre
  45 centroid: (4.04663, 1.6349)
  46 [$img/algorithms/centroid.png]
  47 ]
  48 Note that the centroid might be located in a hole or outside a polygon, easily.
  49 */
  50 //]