使用boost库获取矩形/圆形交点

Question

是否可以得到矩形 x 圆的交点boost？据我所知boost有一个交集函数：

template<typename Geometry1, typename Geometry2, typename GeometryOut>
bool intersection(Geometry1 const & geometry1, Geometry2 const & geometry2, GeometryOut & geometry_out)

但我不知道如何构建圆形几何图形。我的意思是，我可以创建一个具有很多顶点的多边形，但这不是我正在寻找的表示形式

Answer 1

如果你想使用 boost 来获得圆圈，你可以使用boost::geometry::buffer算法。详细信息请参见此处。

您需要传递点作为输入几何图形（圆的中心）和半径作为distance_strategy。完整测试代码如下

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#include <boost/geometry.hpp>
#include <boost/geometry/io/io.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <iostream>

int main()
{
    typedef boost::geometry::model::d2::point_xy<double> point;
    typedef boost::geometry::model::polygon<point> polygon;

    const double buffer_distance = 1.0; // radius of circle
    const int points_per_circle = 36;
    boost::geometry::strategy::buffer::distance_symmetric<double> distance_strategy(buffer_distance);
    boost::geometry::strategy::buffer::join_round join_strategy(points_per_circle);
    boost::geometry::strategy::buffer::end_round end_strategy(points_per_circle);
    boost::geometry::strategy::buffer::point_circle circle_strategy(points_per_circle);
    boost::geometry::strategy::buffer::side_straight side_strategy;

    boost::geometry::model::multi_polygon<polygon> result;

    point pt;
    boost::geometry::read_wkt("POINT(5 5)", pt); // center of circle

    boost::geometry::buffer(pt, result,
                distance_strategy, side_strategy,
                join_strategy, end_strategy, circle_strategy);
    // first item of result is circle with 1 radius and (5,5) point as center
    // result should have 1 polygon
    polygon rect; // your rectangle
    boost::geometry::read_wkt("POLYGON((3 3,3 7,5 7,5 3,3 3))",rect);

    std::deque<polygon> intersectionGeometry;
    boost::geometry::intersection(rect,result.front(),intersectionGeometry);
    if (intersectionGeometry.size() == 1)
        std::cout << boost::geometry::wkt(intersectionGeometry.front()) << std::endl; // intersection

    std::cout << boost::geometry::wkt(result) << "\n";
}

将交集打印为

POLYGON((5 4,4.82635 4.01519,4.65798 4.06031,4.5 4.13397,4.35721 4.23396,4.23396 4.35721,4.13397 4.5,4.06031 4.65798,4.01519 4.82635,4 5,4.01519 5.17365,4.06031 5.34202,4.13397 5.5,4.23396 5.64279,4.35721 5.76604,4.5 5.86603,4.65798 5.93969,4.82635 5.98481,5 6,5 4))

你可以看到result缓冲区的内容是：

MULTIPOLYGON(((6 5,5.98481 4.82635,5.93969 4.65798,5.86603 4.5,5.76604 4.35721,5.64279 4.23396,5.5 4.13397,5.34202 4.06031,5.17365 4.01519,5 4,4.82635 4.01519,4.65798 4.06031,4.5 4.13397,4.35721 4.23396,4.23396 4.35721,4.13397 4.5,4.06031 4.65798,4.01519 4.82635,4 5,4.01519 5.17365,4.06031 5.34202,4.13397 5.5,4.23396 5.64279,4.35721 5.76604,4.5 5.86603,4.65798 5.93969,4.82635 5.98481,5 6,5.17365 5.98481,5.34202 5.93969,5.5 5.86603,5.64279 5.76604,5.76604 5.64279,5.86603 5.5,5.93969 5.34202,5.98481 5.17365,6 5)))

我将图片添加为输出，深色半圆是相交几何：