[英]Intersection of boost::geometry::model::linestring with boost::geometry::model::polygon
我試圖找到多邊形內部的線串部分。 我嘗試了intersection
函數,但它似乎只是找到了實際的交點,而不是與多邊形重疊的線串部分。 有沒有辦法得到這個對象?
這是一個演示情況:
#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;
}
看來您必須使用 multi_linestring 作為輸出類型:
#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;
}
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