Boost.Geometry多邊形點分配

Question

我正在嘗試使用Boost幾何，並且難以將點分配給多邊形。 假設我創建一個點的靜態向量

boost::geometry::model::d2::point_xy<double> >* a; 

然后我創建一個多邊形：

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

假設我已經定義了a點的值。

如何將點從a分配到P？

Answer 1

boost::geometry::assign_points()算法可用於為多邊形分配點范圍。

如果a是點的范圍，而P是多邊形，則將使用：

boost::geometry::assign_points(P, a);

---

這是一個完整的示例，演示了assign_points的用法：

#include <iostream>
#include <vector>
#include <boost/assign/std/vector.hpp>
#include <boost/geometry.hpp>
#include <boost/geometry/algorithms/area.hpp>
#include <boost/geometry/algorithms/assign.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/dsv/write.hpp>

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

    // Create points to represent a 5x5 closed polygon.
    std::vector<point_xy> points;
    points +=
      point_xy(0,0),
      point_xy(0,5),
      point_xy(5,5),
      point_xy(5,0),
      point_xy(0,0)
      ;

    // Create a polygon object and assign the points to it.
    boost::geometry::model::polygon<point_xy> polygon;  
    boost::geometry::assign_points(polygon, points);

    std::cout << "Polygon " << boost::geometry::dsv(polygon) << 
      " has an area of " << boost::geometry::area(polygon) << std::endl;
}

產生以下輸出：

Polygon (((0, 0), (0, 5), (5, 5), (5, 0), (0, 0))) has an area of 25