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
11 //` Shows how to subtract one polygon from another 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
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::list<polygon> output;
37 boost::geometry::difference(green, blue, output);
38
39 int i = 0;
40 std::cout << "green - blue:" << std::endl;
41 BOOST_FOREACH(polygon const& p, output)
42 {
43 std::cout << i++ << ": " << boost::geometry::area(p) << std::endl;
44 }
45
46 /*<-*/ create_svg("difference_a.svg", green, blue, output); /*->*/
47 output.clear();
48 boost::geometry::difference(blue, green, output);
49
50 i = 0;
51 std::cout << "blue - green:" << std::endl;
52 BOOST_FOREACH(polygon const& p, output)
53 {
54 std::cout << i++ << ": " << boost::geometry::area(p) << std::endl;
55 }
56
57 /*<-*/ create_svg("difference_b.svg", green, blue, output); /*->*/
58 return 0;
59 }
60
61 //]
62
63
64 //[difference_output
65 /*`
66 Output:
67 [pre
68 green - blue:
69 0: 0.02375
70 1: 0.542951
71 2: 0.0149697
72 3: 0.226855
73 4: 0.839424
74
75 [$img/algorithms/difference_a.png]
76
77 blue - green:
78 0: 0.525154
79 1: 0.015
80 2: 0.181136
81 3: 0.128798
82 4: 0.340083
83 5: 0.307778
84
85 [$img/algorithms/difference_b.png]
86 ]
87 */
88 //]
89
90
