ceph/src/boost/libs/geometry/example/03_polygon_example.cpp

   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
  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
  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 }