libs/geometry/doc/src/examples/algorithms/sym_difference.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 //[sym_difference
  11 //` Shows how to calculate the symmetric difference (XOR) of two polygons
  12
  13 #include <iostream>
  14
  15 #include <boost/geometry.hpp>
  16 #include <boost/geometry/geometries/polygon.hpp>
  17 #include <boost/geometry/geometries/point_xy.hpp>
  18 #include <boost/geometry/geometries/multi_polygon.hpp>
  19
  20 #include <boost/foreach.hpp>
  21 /*<-*/ #include "create_svg_overlay.hpp" /*->*/
  22
  23 int main()
  24 {
  25     typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;
  26
  27     polygon green, blue;
  28
  29     boost::geometry::read_wkt(
  30         "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)"
  31             "(4.0 2.0, 4.2 1.4, 4.8 1.9, 4.4 2.2, 4.0 2.0))", green);
  32
  33     boost::geometry::read_wkt(
  34         "POLYGON((4.0 -0.5 , 3.5 1.0 , 2.0 1.5 , 3.5 2.0 , 4.0 3.5 , 4.5 2.0 , 6.0 1.5 , 4.5 1.0 , 4.0 -0.5))", blue);
  35
  36     boost::geometry::model::multi_polygon<polygon> multi;
  37
  38     boost::geometry::sym_difference(green, blue, multi);
  39
  40     std::cout
  41         << "green XOR blue:" << std::endl
  42         << "total: " << boost::geometry::area(multi) << std::endl;
  43     int i = 0;
  44     BOOST_FOREACH(polygon const& p, multi)
  45     {
  46         std::cout << i++ << ": " << boost::geometry::area(p) << std::endl;
  47     }
  48
  49     /*<-*/ create_svg("sym_difference.svg", green, blue, multi); /*->*/
  50     return 0;
  51 }
  52
  53 //]
  54
  55
  56 //[sym_difference_output
  57 /*`
  58 Output:
  59 [pre
  60 green XOR blue:
  61 total: 3.1459
  62 0: 0.02375
  63 1: 0.542951
  64 2: 0.0149697
  65 3: 0.226855
  66 4: 0.839424
  67 5: 0.525154
  68 6: 0.015
  69 7: 0.181136
  70 8: 0.128798
  71 9: 0.340083
  72 10: 0.307778
  73
  74 [$img/algorithms/sym_difference.png]
  75
  76 ]
  77 */
  78 //]
  79