1 using System;
  2 using System.Collections.Generic;
  3 using System.Linq;
  4 using System.Text;
  5 using ESRI.ArcGIS.Geometry;
  6 using RGeos.Geometry
  7 
  8 namespace RGeos.Geometry
  9 {
 10     public class CulmulateDistance
 11     {
 12         /// <summary>
 13         /// 点到折线最短距离处距离折线起点的累积距离
 14         /// </summary>
 15         /// <param name="P">任意一点</param>
 16         /// <param name="polyline">折线</param>
 17         /// <returns></returns>
 18         public static double CulmulateDist_Point_to_Polyline(IPoint P, IPolyline polyline)
 19         {
 20             ISegmentCollection segs = polyline as ISegmentCollection;
 21             double min = double.MaxValue;
 22             int segIndex = -1;//最短距离所在档的索引
 23             for (int i = 0; i < segs.SegmentCount; i++)
 24             {
 25                 //点到每条线段的最短距离
 26                 double dis = Dist_Point_to_Segment(P, segs.get_Segment(i));
 27                 if (dis < min)
 28                 {
 29                     min = dis;
 30                     segIndex = i;//取出最小的一个
 31                 }
 32             }
 33             double culmulateDis = 0;
 34             for (int i = 0; i < segs.SegmentCount; i++)
 35             {
 36                 if (segIndex != i)
 37                 {
 38                     culmulateDis += segs.get_Segment(i).Length;
 39                 }
 40                 else
 41                 {
 42                     ISegment current = segs.get_Segment(i);
 43                     Vector3d v = new Vector3d();
 44                     v.X = current.ToPoint.X - current.FromPoint.X;
 45                     v.Y = current.ToPoint.Y - current.FromPoint.Y;
 46 
 47                     Vector3d w = new Vector3d();
 48                     w.X = P.X - current.FromPoint.X;
 49                     w.Y = P.Y - current.FromPoint.Y;
 50 
 51                     double c1 = dot(w, v);//投影长度
 52                     if (c1 <= 0)//这种情况最短距离在该线段的起点处
 53                     {
 54                         break;
 55                     }
 56                     double c2 = dot(v, v);
 57                     if (c2 <= c1)//这种情况最短距离在该线段的终点处                      
 58                     {
 59                         culmulateDis += Math.Sqrt(c2);
 60                         break;
 61                     }
 62 
 63                     double b = c1 / c2;
 64                     culmulateDis += Math.Sqrt(c1);
 65                     IPoint Pb = new PointClass();
 66                     Pb.X = current.FromPoint.X + b * v.X;
 67                     Pb.Y = current.FromPoint.Y + b * v.Y;
 68                     break;
 69                 }
 70             }
 71             return culmulateDis;
 72         }
 73 
 74         public static IPoint GetCentrePoint(IPolygon polygon)
 75         {
 76             IArea pArea = polygon as IArea;
 77             IPoint pt = new PointClass();
 78             pt.X = pArea.Centroid.X;
 79             pt.Y = pArea.Centroid.Y;
 80             return pt;
 81         }
 82 
 83         public static double Dist_Point_to_Segment(IPoint P, ISegment S)
 84         {
 85             Vector3d v = new Vector3d();
 86             v.X = S.ToPoint.X - S.FromPoint.X;
 87             v.Y = S.ToPoint.Y - S.FromPoint.Y;
 88 
 89             Vector3d w = new Vector3d();
 90             w.X = P.X - S.FromPoint.X;
 91             w.Y = P.Y - S.FromPoint.Y;
 92 
 93             double c1 = dot(w, v);
 94             if (c1 <= 0)
 95                 return d(P, S.FromPoint);
 96 
 97             double c2 = dot(v, v);
 98             if (c2 <= c1)
 99                 return d(P, S.ToPoint);
100 
101             double b = c1 / c2;
102             IPoint Pb = new PointClass();
103             Pb.X = S.FromPoint.X + b * v.X;
104             Pb.Y = S.FromPoint.Y + b * v.Y;
105             return d(P, Pb);
106         }
107         /// <summary>
108         /// 向量的模
109         /// </summary>
110         /// <param name="v"></param>
111         /// <returns></returns>
112         public static double norm(Vector3d v)
113         {
114             return Math.Sqrt(dot2(v, v));  // norm = length of vector
115         }
116         /// <summary>
117         /// 2D数量积，点乘
118         /// </summary>
119         /// <param name="u"></param>
120         /// <param name="v"></param>
121         /// <returns></returns>
122         public static double dot2(Vector3d u, Vector3d v)
123         {
124             return ((u).X * (v).X + (u).Y * (v).Y);
125         }
126         public static double dot(Vector3d u, Vector3d v)
127         {
128             return ((u).X * (v).X + (u).Y * (v).Y + (u).Z * (v).Z);
129         }
130 
131         public static double d(IPoint P, IPoint P1)
132         {
133             return Math.Sqrt((P1.X - P.X) * (P1.X - P.X) + (P1.Y - P.Y) * (P1.Y - P.Y));
134         }
135 
136         /// <param name="x">增量X</param>
137         /// <param name="y">增量Y</param>
138         /// <returns>象限角</returns>
139         public static double GetQuadrantAngle(double x, double y)
140         {
141             double theta = Math.Atan(y / x);
142             if (x > 0 && y == 0) return 0;
143             if (x == 0 && y > 0) return Math.PI / 2;
144             if (x < 0 && y == 0) return Math.PI;
145             if (x == 0 && y < 0) return 3 * Math.PI / 2;
146 
147             if (x > 0 && y > 0) return theta;
148             if (x > 0 && y < 0) return Math.PI * 2 + theta;
149             if (x < 0 && y > 0) return theta + Math.PI;
150             if (x < 0 && y < 0) return theta + Math.PI;
151             return theta;
152         }
153     }
154 }

 

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