1 // Boost.Geometry (aka GGL, Generic Geometry Library)
2
3 // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
4 // Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
5 // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
6
7 // Use, modification and distribution is subject to the Boost Software License,
8 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
9 // http://www.boost.org/LICENSE_1_0.txt)
10 //
11 // Polygon Example
12
13 #include <algorithm> // for reverse, unique
14 #include <iostream>
15 #include <string>
16
17 #include <boost/geometry/geometry.hpp>
18 #include <boost/geometry/geometries/point_xy.hpp>
19 #include <boost/geometry/geometries/polygon.hpp>
20 #include <boost/geometry/geometries/adapted/c_array.hpp>
21 #include <boost/geometry/geometries/multi_polygon.hpp>
22
BOOST_GEOMETRY_REGISTER_C_ARRAY_CS(cs::cartesian)23 BOOST_GEOMETRY_REGISTER_C_ARRAY_CS(cs::cartesian)
24
25
26 std::string boolstr(bool v)
27 {
28 return v ? "true" : "false";
29 }
30
main(void)31 int main(void)
32 {
33 using namespace boost::geometry;
34
35 typedef model::d2::point_xy<double> point_2d;
36 typedef model::polygon<point_2d> polygon_2d;
37 typedef model::box<point_2d> box_2d;
38
39 // Define a polygon and fill the outer ring.
40 // In most cases you will read it from a file or database
41 polygon_2d poly;
42 {
43 const double coor[][2] = {
44 {2.0, 1.3}, {2.4, 1.7}, {2.8, 1.8}, {3.4, 1.2}, {3.7, 1.6},
45 {3.4, 2.0}, {4.1, 3.0}, {5.3, 2.6}, {5.4, 1.2}, {4.9, 0.8}, {2.9, 0.7},
46 {2.0, 1.3} // closing point is opening point
47 };
48 assign_points(poly, coor);
49 }
50
51 // Polygons should be closed, and directed clockwise. If you're not sure if that is the case,
52 // call the correct algorithm
53 correct(poly);
54
55 // Polygons can be streamed as text
56 // (or more precisely: as DSV (delimiter separated values))
57 std::cout << dsv(poly) << std::endl;
58
59 // As with lines, bounding box of polygons can be calculated
60 box_2d b;
61 envelope(poly, b);
62 std::cout << dsv(b) << std::endl;
63
64 // The area of the polygon can be calulated
65 std::cout << "area: " << area(poly) << std::endl;
66
67 // And the centroid, which is the center of gravity
68 point_2d cent;
69 centroid(poly, cent);
70 std::cout << "centroid: " << dsv(cent) << std::endl;
71
72
73 // The number of points can be requested per ring (using .size())
74 // or per polygon (using num_points)
75 std::cout << "number of points in outer ring: " << poly.outer().size() << std::endl;
76
77 // Polygons can have one or more inner rings, also called holes, islands, interior rings.
78 // Let's add one
79 {
80 poly.inners().resize(1);
81 model::ring<point_2d>& inner = poly.inners().back();
82
83 const double coor[][2] = { {4.0, 2.0}, {4.2, 1.4}, {4.8, 1.9}, {4.4, 2.2}, {4.0, 2.0} };
84 assign_points(inner, coor);
85 }
86
87 correct(poly);
88
89 std::cout << "with inner ring:" << dsv(poly) << std::endl;
90 // The area of the polygon is changed of course
91 std::cout << "new area of polygon: " << area(poly) << std::endl;
92 centroid(poly, cent);
93 std::cout << "new centroid: " << dsv(cent) << std::endl;
94
95 // You can test whether points are within a polygon
96 std::cout << "point in polygon:"
97 << " p1: " << boolstr(within(make<point_2d>(3.0, 2.0), poly))
98 << " p2: " << boolstr(within(make<point_2d>(3.7, 2.0), poly))
99 << " p3: " << boolstr(within(make<point_2d>(4.4, 2.0), poly))
100 << std::endl;
101
102 // As with linestrings and points, you can derive from polygon to add, for example,
103 // fill color and stroke color. Or SRID (spatial reference ID). Or Z-value. Or a property map.
104 // We don't show this here.
105
106 // Clip the polygon using a box
107 box_2d cb(make<point_2d>(1.5, 1.5), make<point_2d>(4.5, 2.5));
108 typedef std::vector<polygon_2d> polygon_list;
109 polygon_list v;
110
111 intersection(cb, poly, v);
112 std::cout << "Clipped output polygons" << std::endl;
113 for (polygon_list::const_iterator it = v.begin(); it != v.end(); ++it)
114 {
115 std::cout << dsv(*it) << std::endl;
116 }
117
118 typedef model::multi_polygon<polygon_2d> polygon_set;
119 polygon_set ps;
120 union_(cb, poly, ps);
121
122 polygon_2d hull;
123 convex_hull(poly, hull);
124 std::cout << "Convex hull:" << dsv(hull) << std::endl;
125
126 // If you really want:
127 // You don't have to use a vector, you can define a polygon with a deque
128 // You can specify the container for the points and for the inner rings independantly
129
130 typedef model::polygon<point_2d, true, true, std::deque, std::deque> deque_polygon;
131 deque_polygon poly2;
132 ring_type<deque_polygon>::type& ring = exterior_ring(poly2);
133 append(ring, make<point_2d>(2.8, 1.9));
134 append(ring, make<point_2d>(2.9, 2.4));
135 append(ring, make<point_2d>(3.3, 2.2));
136 append(ring, make<point_2d>(3.2, 1.8));
137 append(ring, make<point_2d>(2.8, 1.9));
138 std::cout << dsv(poly2) << std::endl;
139
140 return 0;
141 }
142