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 //[difference_inserter
11 //` Shows how the difference_inserter function can be used
12
13 #include <iostream>
14 #include <vector>
15
16 #include <boost/geometry.hpp>
17 #include <boost/geometry/geometries/point_xy.hpp>
18 #include <boost/geometry/geometries/polygon.hpp>
19
20 #include <boost/foreach.hpp>
21 /*<-*/ #include "create_svg_overlay.hpp" /*->*/
22
main()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 std::vector<polygon> output;
37
38 // Note that this sample simulates the symmetric difference,
39 // which is also available as a separate algorithm.
40 // It chains the output iterator returned by the function to the second instance.
41 boost::geometry::difference_inserter<polygon>
42 (
43 green, blue,
44 boost::geometry::difference_inserter<polygon>
45 (
46 blue, green,
47 std::back_inserter(output)
48 )
49 );
50
51
52 int i = 0;
53 std::cout << "(blue \ green) u (green \ blue):" << std::endl;
54 BOOST_FOREACH(polygon const& p, output)
55 {
56 std::cout << i++ << ": " << boost::geometry::area(p) << std::endl;
57 }
58
59 /*<-*/ create_svg("difference_inserter.svg", green, blue, output); /*->*/
60 return 0;
61 }
62
63 //]
64
65
66 //[difference_inserter_output
67 /*`
68 Output:
69 [pre
70 (blue \\ green) u (green \\ blue):
71 0: 0.525154
72 1: 0.015
73 2: 0.181136
74 3: 0.128798
75 4: 0.340083
76 5: 0.307778
77 6: 0.02375
78 7: 0.542951
79 8: 0.0149697
80 9: 0.226855
81 10: 0.839424
82
83 [$img/algorithms/sym_difference.png]
84
85 ]
86 */
87 //]
88
