detect——point_in_polygon

/******************实现功能：判断平面任一点是否在指定多边形内********************/

 #include <string>
 #include <vector>
 #include <math.h>
 #include <iostream>
 #include <fstream>
 #include <sstream>

 using namespace std;

 typedef struct { int x, y; } Point;

 //算法说明   file:///D:/ddb/相机标定/Point_In_Polygon.pdf
 // a Point is defined by its coordinates {int x, y;}
 //===================================================================

 // isLeft(): tests if a point is Left|On|Right of an infinite line.
 //    Input:  three points P0, P1, and P2
 //    Return: >0 for P2 left of the line through P0 and P1
 //            =0 for P2  on the line
 //            <0 for P2  right of the line
 //    See: Algorithm 1 "Area of Triangles and Polygons"

 inline int
 isLeft(Point P0, Point P1, Point P2)
 {
     return ((P1.x - P0.x) * (P2.y - P0.y)
         - (P2.x - P0.x) * (P1.y - P0.y));
 }

 //==================================================================
 // cn_PnPoly(): crossing number test for a point in a polygon
 //      Input:   P = a point,
 //               V[] = vertex points of a polygon V[n+1] with V[n]=V[0]
 //      Return:  0 = outside, 1 = inside
 // This code is patterned after [Franklin, 2000]
 int
 cn_PnPoly(Point P, Point* V, int n)
 {
     int    cn = ;    // the  crossing number counter

                       // loop through all edges of the polygon
     for (int i = ; i < n; i++)
     {
         // edge from V[i]  to V[i+1]
         if (((V[i].y <= P.y) && (V[i + ].y > P.y))||((V[i].y > P.y) && (V[i + ].y <= P.y)))  // an upward crossing
         {
             // a downward crossing
             // compute  the actual edge-ray intersect x-coordinate
             float vt = (float)(P.y - V[i].y) / (V[i + ].y - V[i].y);
             if (P.x < V[i].x + vt * (V[i + ].x - V[i].x))                // P.x < intersect
                 ++cn;            // a valid crossing of y=P.y right of P.x
         }
     }
     return (cn & );    // 0 if even (out), and 1 if  odd (in)
 }

 // wn_PnPoly(): winding number test for a point in a polygon
 //      Input:   P = a point,
 //               V[] = vertex points of a polygon V[n+1] with V[n]=V[0]
 //      Return:  wn = the winding number (=0 only when P is outside)
 int
 wn_PnPoly(Point P, Point* V, int n)
 {
     int    wn = ;            // the  winding number counter
     // loop through all edges of the polygon
     for (int i = ; i<n; i++)
     {
         // edge from V[i] to  V[i+1]
         if (V[i].y <= P.y)
         {
             // start y <= P.y
             if (V[i + ].y  > P.y)      // an upward crossing
                 if (isLeft(V[i], V[i + ], P) > )  // P left of  edge
                     ++wn;            // have  a valid up intersect
         }
         else
         {                        // start y > P.y (no test needed)
             if (V[i + ].y <= P.y)     // a downward crossing
                 if (isLeft(V[i], V[i + ], P) < )  // P right of  edge
                     --wn;            // have  a valid down intersect
         }
     }
     return wn;
 }

 int
 wn_PnPoly_ddb(Point& P, const std::vector<Point>& V)      // std::vector<Point>& V = vertex points of a polygon V[n + 1] with V[n] = V[0] ,  注意多一个点首尾相同
 {
     int wn = ;            // the  winding number counter
     int n = V.size() - ;                    // loop through all edges of the polygon
     for (int i = ; i<n; i++)
     {
         // edge from V[i] to  V[i+1]
         if (V[i].y <= P.y)
         {
             // start y <= P.y
             if (V[i + ].y  > P.y)      // an upward crossing
                 if (isLeft(V[i], V[i + ], P) > )  // P left of  edge
                     ++wn;            // have  a valid up intersect
         }
         else
         {                        // start y > P.y (no test needed)
             if (V[i + ].y <= P.y)     // a downward crossing
                 if (isLeft(V[i], V[i + ], P) < )  // P right of  edge
                     --wn;            // have  a valid down intersect
         }
     }
     return wn;
 }

 void
 readImageROIpolygen(const std::string& path, std::vector<Point>& pointVec, int i)
 {
     char name[];
     string filename;
     Point p2d;

     int length = sprintf(name, "%d%s", i + , "_ROI.txt");
     filename = path + "/" + name;
     ifstream infile(filename);

     string Fline;
     if (infile) // 有该文件
     {
         while (getline(infile, Fline)) // Fline中不包括每行的换行符
         {
             //cout << Fline << endl;
             string buf;
             stringstream ss(Fline);  // 字符流ss
             vector<string> tokens;  // vector

             // 按照逗号分隔
             while (getline(ss, buf, ','))
             {
                 tokens.push_back(buf);
             }

             ////stringstream  按空格分开字符输入
             //while (ss >> buf)
             //{
             //    tokens.push_back(buf);
             //}

             if (tokens.size()<)
             {
                 continue;
             }
             else if (tokens.size() == )
             {
                 int j = ;
                 p2d.x = atof(tokens[j].c_str());   //根据字段顺序做修改   对应图像 u v
                 j++;
                 p2d.y = atof(tokens[j].c_str());
                 pointVec.push_back(p2d);
             }
         }
         pointVec.push_back(pointVec[]);
         //std::cout << i << endl;
     }
     else // 没有该文件
     {
         cout << "error::  no such file" << endl;
     }
     infile.close();

 }

 /**************** Test ****************/
 void
 main()
 {
     Point detectPoint;
     detectPoint.x = ; //1363, 1260   //2896,2276   //2653,390
     detectPoint.y = ;
     std::string path="矫正后图像";

     std::vector<Point> pointVec;
     readImageROIpolygen(path, pointVec,);
     if (pointVec.size()==)
     {
         cout << "no ROI!!!" << endl;
         return;
     }

     if (wn_PnPoly_ddb(detectPoint, pointVec) == )
     {
         cout << "detectPoint outside ImageROIpolygen!!!!" << endl;
     }
     else
     {
         cout << "detectPoint in ImageROIpolygen!!!!" << endl;
     }

     system("pause");
 }