我正在尝试使用 Boost::Polygon 逐步构建一组多边形。下面代码中的实时数据集取自我在使用 Boost::Polygon 的真实系统中找到的病态输入。
这是最低限度的复制代码（您需要在包含路径中使用 boost 开发标头）：
#include <iostream>
#include <string>
#include <vector>
#include "boost/polygon/polygon.hpp"
using namespace std;
using namespace boost::polygon;
using namespace boost::polygon::operators;
/* Utility function to read a polygon from a string. This is ugly, but works for the purpose of this repro case */
polygon_data<float> readPoly(string str)
{
vector<point_data<float> > result;
size_t index = 0;
while(index != string::npos)
{
size_t xend = str.find(" ", index);
size_t yend = str.find(" ", xend + 1);
float x = atof(str.substr(index, xend - index).c_str());
float y = atof(str.substr(xend + 1, yend - xend + 1).c_str());
result.push_back(point_data<float>(x, y));
if(yend == string::npos)
break;
index = yend + 1;
}
return polygon_data<float>(result.begin(), result.end());
}
/* Utility function to dump a polygon set to cout, useful for visualizing with the python script */
void dumpPoly(vector<polygon_data<float> > polyset)
{
for(vector<polygon_data<float> >::iterator it = polyset.begin(); it != polyset.end(); it++)
{
polygon_data<float> poly = *it;
for(polygon_data<float>::iterator_type jt = poly.begin(); jt != poly.end(); jt++)
{
cout << (*jt).x() << " " << (*jt).y() << " ";
}
cout << endl;
}
}
int main()
{
std::vector<polygon_data<float> > data;
// Construct the polygon set
data += readPoly("-1309.77, 1323.99, -1324, 1309.76, -1324, -1309.76, -1309.77, -1323.99, -1240.23, -1323.99, -1226, -1309.76, -1226, 1309.76, -1240.23, 1323.99");
data += readPoly("-1323.99, -1309.77, -1309.76, -1324, 1309.76, -1324, 1323.99, -1309.77, 1323.99, -1240.23, 1309.76, -1226, -1309.76, -1226, -1323.99, -1240.23");
data += readPoly("1323.99, 1309.77, 1309.76, 1324, -1309.76, 1324, -1323.99, 1309.77, -1323.99, 1240.23, -1309.76, 1226, 1309.76, 1226, 1323.99, 1240.23");
data += readPoly("-544.771, 686.49, -559, 672.261, -559, -544.761, -544.771, -558.99, -475.229, -558.99, -461, -544.761, -461, 672.261, -475.229, 686.49");
data += readPoly("-558.99, -544.771, -544.761, -559, 672.261, -559, 686.49, -544.771, 686.49, -475.229, 672.261, -461, -544.761, -461, -558.99, -475.229");
data += readPoly("686.49, 672.271, 672.261, 686.5, -544.761, 686.5, -558.99, 672.271, -558.99, 602.729, -544.761, 588.5, 672.261, 588.5, 686.49, 602.729");
data += readPoly("-69.8842, -119.057, -49.7607, -119.057, 219.057, 149.76, 219.057, 169.884, 169.884, 219.057, 149.76, 219.057, -119.057, -49.7607, -119.057, -69.8842");
data += readPoly("672.271, -558.99, 686.5, -544.761, 686.5, 672.261, 672.271, 686.49, 602.729, 686.49, 588.5, 672.261, 588.5, -544.761, 602.729, -558.99");
data += readPoly("1309.77, -1323.99, 1324, -1309.76, 1324, 1309.76, 1309.77, 1323.99, 1240.23, 1323.99, 1226, 1309.76, 1226, -1309.76, 1240.23, -1323.99");
/*
This alternative dataset shows that boost.polygon can handle nested holes, to some extent
data += readPoly("100 100 100 1900 1900 1900 1900 100");
data -= readPoly("200 200 200 1800 1800 1800 1800 200");
data += readPoly("300 300 300 1700 1700 1700 1700 300");
data -= readPoly("400 400 400 1600 1600 1600 1600 400");
data += readPoly("500 500 500 1500 1500 1500 1500 500");
data -= readPoly("600 600 600 1400 1400 1400 1400 600");
*/
dumpPoly(data);
return 0;
}
这是我使用 matplotlib 在 python 中编写的一个极小的可视化脚本。只需将上述程序的输出通过管道传输到此脚本，您就会看到结果。它工作正常，我只是将它包括在内以帮助您帮助我:)
#!/usr/bin/env python
import matplotlib.pyplot as plt
import sys
lines = sys.stdin.read().split("\n")
for line in lines:
data = line.split()
if len(data) == 0:
continue
x = []
y = []
i = 0
while i < len(data):
x.append(float(data[i]))
y.append(float(data[i+1]))
i += 2
plt.fill(x, y)
plt.show()
这是我的期望：
这是我得到的：
我的问题是：为什么 Boost::Polygon 会丢弃我的一些输入，我该如何阻止它这样做？