多边形几何对象是否有形态学膨胀操作?
例如,假设我有一个以原点为中心的边长为 1 的正方形(一个带有点 (.5, .5), (-.5, .5) 的 boost::geometry::model::polygon, (-.5, -.5), (.5, -.5) )。如果我用 0.5 的距离/半径“扩张”它,我会得到一个边长为 2 的正方形,仍然以原点为中心。也就是说,多边形的所有边都应沿其法线方向“推出”。
最佳答案
这个术语是“缓冲区”,缓冲多边形仅在 buffer() 的重载中实现,策略为:http://www.boost.org/doc/libs/1_61_0/libs/geometry/doc/html/geometry/reference/algorithms/buffer/buffer_7_with_strategies.html
这是一个将三角形扩大 0.1 个单位的示例。
#include <iostream>
#include <list>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
using coordinate_type = double;
using point_type = boost::geometry::model::d2::point_xy<coordinate_type>;
using polygon_type = boost::geometry::model::polygon<point_type>;
int main()
{
// Construct
polygon_type polygon;
// Counter clock-wise points don't seem to work (no error, but empty output)
// boost::geometry::append(polygon, point_type {0,0});
// boost::geometry::append(polygon, point_type {1,0});
// boost::geometry::append(polygon, point_type {0,1});
// boost::geometry::append(polygon, point_type {0,0});
// Points specified in clockwise order
boost::geometry::append(polygon, point_type {0,0});
boost::geometry::append(polygon, point_type {0,1});
boost::geometry::append(polygon, point_type {1,0});
boost::geometry::append(polygon, point_type {0,0});
//boost::geometry::buffer(poly, output, .5); // THIS_OPERATION_IS_NOT_OR_NOT_YET_IMPLEMENTED
const double buffer_distance = .1;
const int points_per_circle = 36;
boost::geometry::strategy::buffer::distance_symmetric<coordinate_type> 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_type> input;
input.push_back(polygon);
boost::geometry::model::multi_polygon<polygon_type> outputMultiPolygon;
boost::geometry::buffer(polygon, outputMultiPolygon,
distance_strategy, side_strategy,
join_strategy, end_strategy, circle_strategy);
std::cout << outputMultiPolygon.size() << std::endl;
polygon_type outputPolygon = outputMultiPolygon[0];
// Print the points of the result (there are many more than in the input because the corners have been rounded)
for(unsigned int pointID = 0; pointID < outputPolygon.outer().size(); ++pointID) {
std::cout << boost::geometry::get<0>(outputPolygon.outer()[pointID]) << " " << boost::geometry::get<1>(outputPolygon.outer()[pointID]) << std::endl;
}
return 0;
}
关于c++ - 扩大多边形 boost::geometry,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38746894/