我正在尝试使用Boost Polygon库交叉两个多边形。我从boost网站提出的custom_polygon示例开始：
http://www.boost.org/doc/libs/1_59_0/libs/polygon/doc/gtl_custom_polygon.htm
在test_polygon函数中，我填充了两个多边形。我的问题是，是否可以使用poly1和poly2调用交集函数。如果我编译我有一个很长的错误列表。
#include <boost/polygon/polygon.hpp>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <list>
// My Point class
class MyPoint {
public:
double x, y;
};
// MyPolygon as a list of MyPoint
typedef std::list<MyPoint> MyPolygon;
template <>
struct boost::polygon::geometry_concept<MyPoint> {
typedef point_concept type;
};
template <>
struct boost::polygon::point_traits<MyPoint> {
typedef double coordinate_type;
static inline coordinate_type get(const MyPoint& point, boost::polygon::orientation_2d orient) {
if (orient == boost::polygon::HORIZONTAL)
return point.x;
return point.y;
}
};
template <>
struct boost::polygon::point_mutable_traits<MyPoint> {
typedef double coordinate_type;
static inline void set(MyPoint& point, boost::polygon::orientation_2d orient, double value) {
if (orient == boost::polygon::HORIZONTAL)
point.x = value;
else
point.y = value;
}
static inline MyPoint construct(double x_value, double y_value) {
MyPoint retval;
retval.x = x_value;
retval.y = y_value;
return retval;
}
};
template <>
struct boost::polygon::geometry_concept<MyPolygon>{
typedef boost::polygon::polygon_concept type;
};
template <>
struct boost::polygon::polygon_traits<MyPolygon> {
typedef double coordinate_type;
typedef MyPolygon::const_iterator iterator_type;
typedef MyPoint point_type;
static inline iterator_type begin_points(const MyPolygon& t) {
return t.begin();
}
static inline iterator_type end_points(const MyPolygon& t) {
return t.end();
}
// Get the number of sides of the polygon
static inline std::size_t size(const MyPolygon& t) {
return t.size();
}
// Get the winding direction of the polygon
static inline winding_direction winding(const MyPolygon& t) {
return unknown_winding;
}
};
template <>
struct boost::polygon::polygon_mutable_traits<MyPolygon> {
//expects stl style iterators
template < typename iT >
static inline MyPolygon& set_points(MyPolygon& t, iT input_begin, iT input_end) {
t.clear();
t.insert(t.end(), input_begin, input_end);
return t;
}
};
template < typename Polygon, typename Point >
void test_polygon() {
Polygon poly1, poly2;
// Define a vector container
std::vector< boost::polygon::polygon_traits< Polygon >::point_type > vpoints;
vpoints.push_back(boost::polygon::construct<Point>(0.0, 0.0));
vpoints.push_back(boost::polygon::construct<Point>(0.0, 1.0));
vpoints.push_back(boost::polygon::construct<Point>(1.0, 1.0));
vpoints.push_back(boost::polygon::construct<Point>(1.0, 0.0));
vpoints.push_back(boost::polygon::construct<Point>(0.05, 0.0));
boost::polygon::set_points(poly1, vpoints.begin(), vpoints.end());
vpoints.clear();
vpoints.push_back(boost::polygon::construct<Point>(0.5, -0.5));
vpoints.push_back(boost::polygon::construct<Point>(0.5, 0.5));
vpoints.push_back(boost::polygon::construct<Point>(1.5, 0.5));
vpoints.push_back(boost::polygon::construct<Point>(1.5, -0.5));
vpoints.push_back(boost::polygon::construct<Point>(0.5, -0.5));
boost::polygon::set_points(poly2, vpoints.begin(), vpoints.end());
std::deque<Polygon> output;
boost::geometry::intersection(poly1, poly2, output); // ERROR!!!
}
int main() {
test_polygon< MyPolygon, MyPoint >();
system("pause");
return 0;
}
你似乎混淆了两个boost库。
这是使用Boost Geometry的快速改编：
#include <boost/geometry.hpp>
#include <boost/geometry/core/point_type.hpp>
#include <boost/geometry/geometries/point.hpp>
#include <boost/geometry/geometries/register/point.hpp>
#include <boost/geometry/geometries/register/linestring.hpp>
namespace bg = boost::geometry;
struct MyPoint {
double x, y;
};
typedef std::vector<MyPoint> MyPolygon;
BOOST_GEOMETRY_REGISTER_POINT_2D(MyPoint, double, bg::cs::cartesian, x, y)
BOOST_GEOMETRY_REGISTER_LINESTRING(MyPolygon)
template < typename Polygon, typename Point >
std::deque<Polygon> test_polygon() {
Polygon poly1 { {0.0, 0.0}, {0.0, 1.0}, {1.0, 1.0}, {1.0, 0.0}, {0.05, 0.0}, };
Polygon poly2 { {0.5, -0.5}, {0.5, 0.5}, {1.5, 0.5}, {1.5, -0.5}, {0.5, -0.5}, };
std::deque<Polygon> output;
boost::geometry::intersection(poly1, poly2, output);
return output;
}
int main() {
for (auto& p : test_polygon< MyPolygon, MyPoint >())
std::cout << "Intersection: " << bg::wkt(p) << "\n";
}
打印：
Intersection: LINESTRING(1 0.5,1 0.5)
Intersection: LINESTRING(0.5 0,0.5 0)
我用list替换了vector，因为* REGISTER_LINESTRING宏需要随机访问迭代器。如果你真的可以帮助它成为std::list，你可以走“复杂”的路线，但这可能会使算法效率低下：