c++ - 为什么 boost::geometry::intersection 不能正常工作？

Question

我为 Boost Geometry 交集函数编写了下一个测试函数

typedef boost::geometry::model::polygon<boost::tuple<int, int> > Polygon;

void test_boost_intersection() {
  Polygon green, blue;
  boost::geometry::read_wkt("POLYGON((0 0,0 9,9 9,9 0,0 0))", green);
  boost::geometry::read_wkt("POLYGON((2 2,2 9,9 9,9 2,2 2))", blue);
  std::deque<Polygon> output;
  boost::geometry::intersection(green, blue, output);
  BOOST_FOREACH(Polygon const& p, output)
  {
    std::cout << boost::geometry::dsv(p) << std::endl;
  }
};

我期望输出结果为:

(((2, 2), (2, 9), (9, 9), (9, 2), (2, 2)))

但是我得到了:

((((1, 9), (9, 9), (9, 2), (2, 2), (1, 9))))

我使用 Boost 1.54。

如果我更改第一个多边形，交叉点工作正常。

编辑:当我将多边形类型更改为

boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> >

它开始正常工作。那么我不能一直使用以前的类型吗？

Answer 1

您需要 correct 满足算法前提条件的输入多边形: Live On Coliru 打印

(((2, 9), (9, 9), (9, 2), (2, 2), (2, 9)))

#include <boost/tuple/tuple.hpp>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/geometries/adapted/boost_tuple.hpp>
#include <boost/foreach.hpp>
typedef boost::geometry::model::polygon<boost::tuple<int, int> > Polygon;

BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian)

void test_boost_intersection() {
    Polygon green, blue;
    boost::geometry::read_wkt("POLYGON((0 0,0 9,9 9,9 0,0 0))", green);
    boost::geometry::read_wkt("POLYGON((2 2,2 9,9 9,9 2,2 2))", blue);
    boost::geometry::correct(green);
    boost::geometry::correct(blue);
    std::deque<Polygon> output;
    boost::geometry::intersection(green, blue, output);
    BOOST_FOREACH(Polygon const& p, output)
    {
        std::cout << boost::geometry::dsv(p) << std::endl;
    }
}

int main()
{
    test_boost_intersection();
}