C++ boost:：geometry:：联合无结果

我试图使用boost:：geometry:：union合并一些多边形，但对于某些条目，输出向量为空

以下是一个例子：

#include <iostream>
#include <vector>

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>

#include <boost/foreach.hpp>

int main()
{
    typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;

polygon green, blue;

boost::geometry::read_wkt(
    "POLYGON((440820.110024126 4047009.80267429, 440806.545727707 4046942.39533656, 440797.171880196 4046895.8425726, 440804.202135392 4046888.73092639, 440813.573458131 4046935.27114371, 440827.140279322 4047002.69102807))", green);

boost::geometry::read_wkt(
    "POLYGON((440855.857887967 4046932.1248641, 440813.740724389 4046942.21109839, 440806.376538684 4046935.44583646, 440848.493702262 4046925.35960217))", blue);


if(boost::geometry::area(green) < 0) boost::geometry::reverse(green);
if(boost::geometry::area(blue) < 0 ) boost::geometry::reverse(blue);


std::vector<polygon> output;
boost::geometry::union_(green, blue, output);

std::cout << " output size is : " << output.size() << std::endl;

int i = 0;
std::cout << "green || blue:" << std::endl;

BOOST_FOREACH(polygon const& p, output)
{
    std::cout << i++ << ": " << boost::geometry::area(p) << std::endl;
}

system("pause");
return 0;
}

---

这是此函数中的错误还是我的代码中有错误？

为了提高效率，假设输入是“规范化”或“规范化”的

因此，您必须确保输入多边形为：

correct(green);
correct(blue);

boost::geometry::union_(green, blue, output);

int i = 0;
for(polygon const& p: output)
{
    std::cout << i++ << ": " << boost::geometry::area(p) << "\n";
    std::cout << "Shape: " << dsv(p) << "\n";
}

---

谢谢，我在这里被封锁了四天，谢谢。请问，有没有关于union算法如何工作的解释？文档：函数

union

和我猜的<代码>正确

correct(green);
correct(blue);

boost::geometry::union_(green, blue, output);

int i = 0;
for(polygon const& p: output)
{
    std::cout << i++ << ": " << boost::geometry::area(p) << "\n";
    std::cout << "Shape: " << dsv(p) << "\n";
}

#include <iostream>
#include <vector>

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>

#include <boost/foreach.hpp>

int main()
{
    typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;
    using boost::geometry::correct;
    using boost::geometry::dsv;

    polygon green, blue;

    boost::geometry::read_wkt(
            "POLYGON((440820.110024126 4047009.80267429, 440806.545727707 4046942.39533656, 440797.171880196 4046895.8425726, 440804.202135392 4046888.73092639, 440813.573458131 4046935.27114371, 440827.140279322 4047002.69102807))", 
            green);
    boost::geometry::read_wkt(
            "POLYGON((440855.857887967 4046932.1248641, 440813.740724389 4046942.21109839, 440806.376538684 4046935.44583646, 440848.493702262 4046925.35960217))", 
            blue);

    correct(green);
    correct(blue);

    std::vector<polygon> output;
    boost::geometry::union_(green, blue, output);

    int i = 0;
    BOOST_FOREACH(polygon const& p, output)
    {
        std::cout << i++ << ": " << boost::geometry::area(p) << "\n";
        std::cout << "Shape: " << dsv(p) << "\n";
    }
}