Boost polygon intersection API运行结果与预期相反问题求助

• 根因：Boost Geometry对输入多边形的顶点环绕方向、闭合性有严格格式要求，默认model::polygon要求顶点为顺时针环绕，若输入多边形不符合该规范，会被库判定内外区域颠倒，最终得到反向的交集结果。
• 解决方案：完成WKT读入后，调用boost::geometry::correct()接口对两个多边形做格式修正，该接口会自动适配模板定义的环绕规则调整顶点顺序、补全闭合、移除重复顶点，符合库的运算要求。

修改后的核心代码如下：

typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon;
 
polygon a, b;

boost::geometry::read_wkt("POLYGON((422.029 420.829,416.779 427.824,413.079 432.754,411.514 434.839,405.294 443.123,367.717 493.174,361.119 501.961,359.867 503.693,349.783 498.44,328.039 487.113,312.182 481.212,295.134 477.466,278.859 475.139,266.868 475.801,187.698 491.788,166.692 495.595,157.994 464.487,147.902 436.336,139.553 416.747,117.365 366.518,95.1775 316.288,68.2962 245.995,45.4972 177.281,31.9009 125.252,24.7675 98.0465,7.031 30.4037,-5.09537 -23.5814,-13.3492 -74.931,-22.0924 -132.107,-30.068 -226.135,-30.8215 -230.193,-33.1719 -318.815,-35.5218 -407.437,-19.2902 -403.222,36.0998 -393.283,126.809 -387.227,145.351 -390.15,164.088 -394.348,231.549 -417.759,299.009 -441.17,298.703 -456.121,302.675 -457.547,346.766 -473.386,395.71 -490.966,444.654 -508.547,456.541 -512.812,475.159 -513.201,481.397 -513.329,485.21 -513.408,490.793 -513.523,508.346 -513.874,508.437 -513.876,515.036 -514.009,517.093 -514.051,524.719 -514.205,604.376 -529.072,619.023 -527.544,640.877 -516.607,706.036 -517.941,771.196 -519.276,773.204 -519.323,773.291 -515.039,755.121 -444.833,734.542 -425.062,730.418 -414.227,750.154 -385.311,751.05 -303.546,749.413 -300.971,751.095 -299.408,803.104 -251.069,855.113 -202.731,892.855 -140.167,930.598 -77.6028,939.232 -69.3115,938.067 -67.6543,905.009 -20.5411,871.951 26.572,816.821 105.141,761.691 183.71,706.561 262.28,702.345 264.782,675.313 280.828,671.489 283.098,670.221 282.255,626.86 253.44,583.5 224.624,545.885 184.348,508.27 144.071,470.699 141.098,468.429 140.919,466.877 142.813,406.125 216.993,394.011 244.292,392.277 261.076,357.41 315.935,359.299 316.721,412.859 339.189,466.419 361.656,465.655 362.675,465.175 363.315,465.094 363.422,464.335 364.435,460.925 368.981,450.837 382.429,447.236 387.23,443.635 392.03,440.034 396.83,436.434 401.63,432.832 406.431,429.231 411.23,425.63 416.03,422.029 420.829))", a);
boost::geometry::read_wkt("POLYGON((0 504,861 504,861 -0,0 -0,0 504))", b);

// 新增两行修正代码即可解决问题
boost::geometry::correct(a);
boost::geometry::correct(b);

std::deque<polygon> output;
boost::geometry::intersection(a, b, output);

修正后运行代码，取消注释原始多边形的绘制代码，即可验证输出的output区域为两个多边形的正确交集。

内容的提问来源于stack exchange，提问作者TestUser