1 public struct Point
2 {
3 public float x;
4
5 public float y;
6 }
7
8 public class PolygonHelper
9 {
10 /// <summary>
11 /// 判断目标点是否在多边形内
12 /// </summary>
13 /// <param name="targetPoint">目标点</param>
14 /// <param name="polygonPoints">多边形点集合</param>
15 /// <returns></returns>
16 public static bool IsInPolygon(Point targetPoint, List<Point> polygonPoints)
17 {
18 if (polygonPoints == null || polygonPoints.Count < 2) return false;
19 int ncross = 0;
20 for (int i = 0; i < polygonPoints.Count; i++)
21 {
22 Point p1 = polygonPoints[i];
23 Point p2 = polygonPoints[(i + 1) % polygonPoints.Count]; //相邻两条边p1,p2
24 if (p1.y == p2.y)
25 continue;
26 if (targetPoint.y < Math.Min(p1.y, p2.y))
27 continue;
28 if (targetPoint.y >= Math.Max(p1.y, p2.y))
29 continue;
30 double x = (targetPoint.y - p1.y) * (p2.x - p1.x) / (p2.y - p1.y) + p1.x;
31 if (x > targetPoint.x)//
32 ncross++;
33 }
34 return (ncross % 2 == 1);
35 }
36 }
