boost :: geometry :: model :: linestringとboost :: geometry :: model :: polygonの交点

Question

ポリゴンの内側にある線ストリングの部分を探しようとしています。私はintersection関数を試しましたが、ポリゴンと重なっている線ストリングの部分ではなく、実際の交差点を見つけるようです。このオブジェクトを取得する方法はありますか？

ここ

はデモの状況です：

#include <iostream> 
#include <fstream> 

#include <boost/geometry.hpp> 
#include <boost/geometry/geometries/point_xy.hpp> 
#include <boost/geometry/geometries/polygon.hpp> 
#include <boost/geometry/io/svg/svg_mapper.hpp> 
#include <boost/geometry/geometries/linestring.hpp> 

using point_type = boost::geometry::model::d2::point_xy<double>; 
using polygon_type = boost::geometry::model::polygon<point_type>; 
using linestring_type = boost::geometry::model::linestring<point_type>; 

int main() 
{ 
    polygon_type polygon; 

    polygon.outer().push_back(point_type{10,10}); 
    polygon.outer().push_back(point_type{12,10}); 
    polygon.outer().push_back(point_type{12,12}); 
    polygon.outer().push_back(point_type{10,12}); 
    polygon.outer().push_back(point_type{10,10}); 

    linestring_type linestring; 
    linestring.push_back(point_type{11,9}); 
    linestring.push_back(point_type{11,11}); 
    linestring.push_back(point_type{13,11}); 

    // Expected intersections at (11, 10) and (12, 11) 

    std::ofstream svg("both.svg"); 

    linestring_type output; 
    boost::geometry::intersection(polygon, linestring, output); 

    for(auto iter = output.begin(); iter != output.end(); ++iter) { 
     std::cout << boost::geometry::get<0>(*iter) << " " << boost::geometry::get<1>(*iter) << std::endl; 
    } 
// The output is: 
// 11 10 
// 12 11 

// But I want it to be: 
// 11 10 
// 11 11 
// 12 11 
    return 0; 
} 

Answer 1

あなたが出力タイプとしてmulti_linestringを使用しなければならないことが表示されます：

#include <iostream> 

#include <boost/geometry.hpp> 
#include <boost/geometry/geometries/point_xy.hpp> 
#include <boost/geometry/geometries/polygon.hpp> 
#include <boost/geometry/geometries/linestring.hpp> 
#include <boost/geometry/multi/geometries/multi_linestring.hpp> 

using point_type = boost::geometry::model::d2::point_xy<double>; 
using polygon_type = boost::geometry::model::polygon<point_type>; 
using linestring_type = boost::geometry::model::linestring<point_type>; 
using multi_linestring_type = boost::geometry::model::multi_linestring<linestring_type>; 

int main() 
{ 
    polygon_type polygon; 

    polygon.outer().push_back(point_type{10,10}); 
    polygon.outer().push_back(point_type{10,12}); 
    polygon.outer().push_back(point_type{12,12}); 
    polygon.outer().push_back(point_type{12,10}); 
    polygon.outer().push_back(point_type{10,10}); 

    linestring_type linestring; 
    linestring.push_back(point_type{11,9}); 
    linestring.push_back(point_type{11,11}); 
    linestring.push_back(point_type{13,11}); 

    // Expected intersections at (11, 10) and (12, 11) 

    multi_linestring_type intersection; 
    boost::geometry::intersection(polygon, linestring, intersection); 

    for(auto intersectionIter = intersection.begin(); intersectionIter != intersection.end(); ++intersectionIter) { 
     linestring_type intersectionPiece = *intersectionIter; 
     std::cout << "Piece:" << std::endl; 
     for(auto intersectionPieceIter = intersectionPiece.begin(); intersectionPieceIter != intersectionPiece.end(); ++intersectionPieceIter) { 
      std::cout << boost::geometry::get<0>(*intersectionPieceIter) << " " << boost::geometry::get<1>(*intersectionPieceIter) << std::endl; 
     } 

    } 

    return 0; 
}