多边形中的提升点会产生错误结果？

Question

我进行了以下单元测试，两次检查失败：

BOOST_AUTO_TEST_CASE(test_point_in_polygon)
{
    typedef boost::geometry::model::d2::point_xy<double> point_type;
    boost::geometry::model::polygon<point_type> poly;
    boost::geometry::read_wkt("POLYGON((-57.0635 -3.58045, -57.8088 -4.75336, -56.7036 -7.65533, -56.4646 -9.08261, -55.219 -9.42072, -54.6047 -9.54237, -53.868 -9.22164, -52.4139 -8.58345, -49.4691 -6.94159, -49.2295 -6.87687, -47.1079 -6.18013, -45.9159 -5.91411, -43.7897 -5.89581, -42.285 -5.95883, -40.1693 -6.38999, -38.1374 -6.87424, -35.7062 -7.67065, -34.6193 -8.40713, -34.1769 -8.74957, -31.785 -9.31504, -30.574 -9.70903, -26.909 -10.5865, -24.9817 -11.268, -22.6134 -12.2833, -21.0927 -13.3427, -20.006 -13.7029, -16.8407 -15.2466, -13.2203 -16.816, -11.3922 -17.4133, -10.7577 -17.6366, -8.54581 -18.2736, -7.18058 -18.6037, -4.86031 -19.0997, -4.25834 -19.3046, -3.39545 -19.3122, -0.985195 -19.7047, -0.340967 -19.9409, 0.75209 -19.8968, 3.30498 -20.3562, 6.82228 -20.6405, 10.4384 -20.5995, 13.8557 -20.2595, 14.7523 -20.1371, 18.3468 -19.4284, 18.9915 -19.4505, 22.5377 -18.5053, 23.2192 -18.4658, 26.4885 -17.3378, 27.2915 -17.2273, 30.5962 -15.8816, 32.7278 -14.6911, 33.8878 -14.1893, 36.2752 -12.7482, 38.5306 -11.1893, 40.8465 -9.28305, 41.1732 -9.05935, 43.372 -7.07535, 45.2436 -5.2073, 46.9925 -3.21699, 48.616 -1.35438, 50.628 0.592424, 52.158 1.37445, 53.1148 2.07603, 50.9152 5.07491, 50.3177 6.38521, 49.9412 7.3891, 48.8311 9.29466, 47.7653 12.692, 45.6416 16.3693, 43.7106 17.9319, 41.4998 17.9314, 37.4335 19.4761, 34.3477 18.4887, 32.1299 18.0676, 29.2684 18.0666, 26.5269 15.0811, 19.7706 14.5304, 15.8916 12.9664, 14.8124 12.5622, 12.783 10.0368, 12.4488 9.65713, 11.1008 7.47097, 8.9187 5.4486, 5.63935 1.10272, -6.34225 4.45488, -8.60563 7.7494, -16.2454 11.2148, -23.399 18.8388, -25.8497 20.2781, -28.8931 22.7068, -31.4379 22.8942, -32.5636 21.9563, -35.2968 20.2469, -37.3132 19.0133, -37.9703 18.2828, -40.4433 15.553, -40.9543 14.1728, -42.8783 10.3486, -46.3297 7.28714, -48.959 5.88183, -52.1939 2.65934, -54.8196 -0.896786))", poly);

    point_type point (-57.8088, -1.5755);
    BOOST_CHECK_EQUAL(boost::geometry::within(point, poly), false);

    point = point_type(-100, -2);
    BOOST_CHECK_EQUAL(boost::geometry::within(point, poly), false);

}

数据如下所示：

我的使用方式与文档（http://www.boost.org/doc/libs/1_61_0/libs/geometry/doc/html/geometry/reference/algorithms/within/within_2.html）类似。

如图所示，很明显两个点都在多边形之外。 我做错了什么，或者我在提升中发现了一个错误？

Answer 1

问题是由您使用的多边形类型（您提供的多边形数据）不匹配引起的。使用boost::geometry::model::polygon<point_type>创建一个多边形，其点类型为point_type，顺时针方向为已关闭，其他一些由默认模板参数配置。在您提供的数据中，第一个点不等于最后一个点（这是此上下文中closed的定义）。您可以make your polygon not be closed (polygon<point_type,true,false>)或make sure that your first and last points are equal (by copying the first point at the end)。

编辑：另一种（可能更好）的方法可能是使用boost::geometry::correct(poly);，而无需更改任何其他内容，如此（非常有趣）answer。