boost :: geometry :: union没有结果 [英] boost::geometry::union no result
问题描述
我正在尝试使用boost :: geometry :: union_合并一些多边形,但是某些条目的输出向量为空.
I'm trying to merge some polygons using boost::geometry::union_ but the output vector is empty for some entries.
这是一个示例:
#include <iostream>
#include <vector>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>
#include <boost/foreach.hpp>
int main()
{
typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;
polygon green, blue;
boost::geometry::read_wkt(
"POLYGON((440820.110024126 4047009.80267429, 440806.545727707 4046942.39533656, 440797.171880196 4046895.8425726, 440804.202135392 4046888.73092639, 440813.573458131 4046935.27114371, 440827.140279322 4047002.69102807))", green);
boost::geometry::read_wkt(
"POLYGON((440855.857887967 4046932.1248641, 440813.740724389 4046942.21109839, 440806.376538684 4046935.44583646, 440848.493702262 4046925.35960217))", blue);
if(boost::geometry::area(green) < 0) boost::geometry::reverse(green);
if(boost::geometry::area(blue) < 0 ) boost::geometry::reverse(blue);
std::vector<polygon> output;
boost::geometry::union_(green, blue, output);
std::cout << " output size is : " << output.size() << std::endl;
int i = 0;
std::cout << "green || blue:" << std::endl;
BOOST_FOREACH(polygon const& p, output)
{
std::cout << i++ << ": " << boost::geometry::area(p) << std::endl;
}
system("pause");
return 0;
}
当我绘制获得的两个多边形时:
when I drew the two polygons I obtained :
但是上面代码的结果是:
but the result of the code above was :
output size is : 0
green || blue:
Press any key to continue . . .
这是该功能的错误还是我的代码有错误?
is this a bug in this function or there is a mistake in my code ?
推荐答案
Boost Geomwetry算法出于效率考虑,假设输入为规范化"或规范化".
Boost Geomwetry algorithms, for efficiency, assume that input is 'normalized' or 'canonical'.
因此,您必须确保输入的多边形为:
So you have to make sure that your input polygons are:
correct(green);
correct(blue);
boost::geometry::union_(green, blue, output);
int i = 0;
for(polygon const& p: output)
{
std::cout << i++ << ": " << boost::geometry::area(p) << "\n";
std::cout << "Shape: " << dsv(p) << "\n";
}
打印:
0:1289.08
形状:((((440813,4.04693e + 06),(440804,4.04689e + 06),(440797,4.0469e + 06),(440807,4.04694e + 06),(440820,4.04701e + 06),(440827、4.047e + 06),(440815、4.04694e + 06),(440856、4.04693e + 06),(440848、4.04693e + 06),(440813、4.04693e + 06)))代码>
查看 在Coliru上直播
See it Live on Coliru
#include <iostream>
#include <vector>
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/io/wkt/wkt.hpp>
#include <boost/foreach.hpp>
int main()
{
typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;
using boost::geometry::correct;
using boost::geometry::dsv;
polygon green, blue;
boost::geometry::read_wkt(
"POLYGON((440820.110024126 4047009.80267429, 440806.545727707 4046942.39533656, 440797.171880196 4046895.8425726, 440804.202135392 4046888.73092639, 440813.573458131 4046935.27114371, 440827.140279322 4047002.69102807))",
green);
boost::geometry::read_wkt(
"POLYGON((440855.857887967 4046932.1248641, 440813.740724389 4046942.21109839, 440806.376538684 4046935.44583646, 440848.493702262 4046925.35960217))",
blue);
correct(green);
correct(blue);
std::vector<polygon> output;
boost::geometry::union_(green, blue, output);
int i = 0;
BOOST_FOREACH(polygon const& p, output)
{
std::cout << i++ << ": " << boost::geometry::area(p) << "\n";
std::cout << "Shape: " << dsv(p) << "\n";
}
}
这篇关于boost :: geometry :: union没有结果的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!