c++ - Boost.Geometry 多边形点赋值

Question

我正在尝试使用 boost 几何体，但在将点分配给多边形时遇到了问题。假设我创建了一个点的静态 vector

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

然后我创建一个多边形:

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

假设我已经定义了 a 的点的值。

我如何分配点从 a 到 P？

Answer 1

boost::geometry::assign_points()算法可用于将一系列点分配给多边形。

如果 a 是点的范围并且 P 是多边形，那么可以使用:

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

---

这是一个完整的 example演示 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;
}

产生以下输出:

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