Boost :: Geometry：如何在multi_polygon中连接相交的多边形？

Question

所以我想在多边形中加入所有相互关联的多边形。怎么办这样的事情？

我们想要优化这样的图像（一个绿色multi_polygon）（我们可以看到黄色虚线 - 显然是在multi_polygon的每个poligon上执行的简化的结果，而不是在multi_polygon上）

这里有可编译的代码来生成这样的图像：

#include <iostream>
#include <fstream>
#include <boost/assign.hpp>

#include <boost/algorithm/string.hpp>
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>

#include <boost/geometry/extensions/io/svg/svg_mapper.hpp>

template <typename Geometry1, typename Geometry2>
void create_svg(std::string const& filename, Geometry1 const& a, Geometry2 const& b)
{
    typedef typename boost::geometry::point_type<Geometry1>::type point_type;
    std::ofstream svg(filename.c_str());

    boost::geometry::svg_mapper<point_type> mapper(svg, 400, 400);
    mapper.add(a);
    mapper.add(b);

    mapper.map(a, "fill-opacity:0.5;fill:rgb(153,204,0);stroke:rgb(153,204,0);stroke-width:2");
    mapper.map(b, "opacity:0.8;fill:none;stroke:rgb(255,128,0);stroke-width:4;stroke-dasharray:1,7;stroke-linecap:round");
}


boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > make_point(int x, int y)
{
    boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > return_item;
    boost::geometry::model::d2::point_xy<double> p1(x, y);
    boost::geometry::model::d2::point_xy<double> p2(x-1, y);
    boost::geometry::model::d2::point_xy<double> p3(x-1, y-1);
    boost::geometry::model::d2::point_xy<double> p4(x, y-1);

    boost::geometry::append(  return_item, p1);
    boost::geometry::append(  return_item, p2);
    boost::geometry::append(  return_item, p3);
    boost::geometry::append(  return_item, p4);

    return return_item;

}

int main()
{
    // create a container for joined points structure
    boost::geometry::model::multi_polygon< boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > > output, simpl;

    // join points one by one (because one day we would have many=))
    output.push_back(make_point(1,1));
    boost::geometry::correct(output);

    output.push_back(make_point(2,1));
    boost::geometry::correct(output);

    output.push_back(make_point(3,1));
    boost::geometry::correct(output);

    output.push_back(make_point(4,1));
    boost::geometry::correct(output);

    output.push_back(make_point(5,1));
    boost::geometry::correct(output);

    output.push_back(make_point(2,2));
    boost::geometry::correct(output);

    output.push_back(make_point(3,2));
    boost::geometry::correct(output);

    output.push_back(make_point(5,2));
    boost::geometry::correct(output);

    output.push_back(make_point(5,5));
    boost::geometry::correct(output);


    // simplify joined structure
    boost::geometry::simplify(output, simpl, 0.5);

    // create an svg image
    create_svg("make_envelope.svg",  output, simpl );
}

需要至少从boost/geometry/extensions/io/svg/提升1.47.0和3个文件

我需要的是简单的：如何将相互关联的poligons分组？在这种情况下，我们将在我们的multy_poligon中获得2个poligons，如此处所示 - 红色和绿色：

Update:

所以我在dissolve上找到了这个信息，并创建了使用环创建cels的示例代码：

#include <iostream>
#include <fstream>
#include <boost/assign.hpp>

//Boost
#include <boost/algorithm/string.hpp>
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>
#include <boost/geometry/geometries/adapted/boost_tuple.hpp>

BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian)

#include <boost/foreach.hpp>

//Boost Geometry extensions (from trunk) 
#include <boost/geometry/extensions/io/svg/svg_mapper.hpp>

template <typename Geometry1, typename Geometry2>
void create_svg(std::string const& filename, Geometry1 const& a, Geometry2 const& b)
{
    typedef typename boost::geometry::point_type<Geometry1>::type point_type;
    std::ofstream svg(filename.c_str());

    boost::geometry::svg_mapper<point_type> mapper(svg, 400, 400);
    mapper.add(a);
    mapper.add(b);

    mapper.map(a, "fill-rule:nonzero;fill-opacity:0.5;fill:rgb(153,204,0);stroke:rgb(153,204,0);stroke-width:2;");
    mapper.map(b, "opacity:0.8;fill:none;stroke:rgb(255,128,0);stroke-width:4;stroke-dasharray:1,7;stroke-linecap:round");
}

void make_point(int x, int y, boost::geometry::model::ring<boost::geometry::model::d2::point_xy<double> > & ring)
{
    using namespace boost::assign;

    ring += 
        boost::geometry::model::d2::point_xy<double>(x-1, y-1),
        boost::geometry::model::d2::point_xy<double>(x, y-1),
        boost::geometry::model::d2::point_xy<double>(x, y),
        boost::geometry::model::d2::point_xy<double>(x-1, y),
        boost::geometry::model::d2::point_xy<double>(x-1, y-1);

}

int main()
{
    using namespace boost::assign;
    boost::geometry::model::ring<boost::geometry::model::d2::point_xy<double> > ring0, ring1,ring;

    boost::geometry::model::multi_polygon< boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > > outputw;

    make_point(1, 1, ring) ;
    make_point(2, 1, ring) ;
    make_point(3, 1, ring) ;
    make_point(4, 1, ring) ;
    make_point(5, 1, ring) ;
    make_point(2, 2, ring) ;
    make_point(3, 2, ring) ;
    make_point(5, 2, ring) ;

    boost::geometry::model::ring<boost::geometry::model::d2::point_xy<double> > output;
    boost::geometry::simplify(ring, output, 1);

    // create an svg image
    create_svg("make_envelope.svg",  ring, output );
}

它返回这样的环形图像：

如果我们可以使用溶解将它变成poligon，这将真正解决我的一些问题。但看起来目前我们不能因为这个编译器错误问题描述here

Answer 1

怎么用Qt。如果您使用QPolygonF，您可以调用unite，它可以完全满足您的需求。在齐声之后，您可以提取点并将它们放回您的增强容器中。

如果qt不是一个选项，请看看这里提出的算法http://www.wykobi.com

Answer 2

您可以使用boost库中的此功能：

void union_(Geometry1 const & geometry1, Geometry2 const & geometry2, Collection & output_collection)

如果它们有交叉点或者将它们放入一个集合（矢量，双端队列等），它需要两个几何并将它们组合在一起（如果没有）。