计算一个点是否落在多边形内 

 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     }

 

posted @ 2021-01-25 14:46  荀幽  阅读(180)  评论(0)    收藏  举报