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 = 0;    // the  crossing number counter

                      // loop through all edges of the polygon
    for (int i = 0; i < n; i++)
    {    
        // edge from V[i]  to V[i+1]
        if (((V[i].y <= P.y) && (V[i + 1].y > P.y))||((V[i].y > P.y) && (V[i + 1].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 + 1].y - V[i].y);
            if (P.x < V[i].x + vt * (V[i + 1].x - V[i].x))                // P.x < intersect
                ++cn;            // a valid crossing of y=P.y right of P.x
        }
    }
    return (cn & 1);    // 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 = 0;            // the  winding number counter
    // loop through all edges of the polygon
    for (int i = 0; i<n; i++) 
    {                    
        // edge from V[i] to  V[i+1]
        if (V[i].y <= P.y) 
        {         
            // start y <= P.y
            if (V[i + 1].y  > P.y)      // an upward crossing
                if (isLeft(V[i], V[i + 1], P) > 0)  // P left of  edge
                    ++wn;            // have  a valid up intersect
        }
        else 
        {                        // start y > P.y (no test needed)
            if (V[i + 1].y <= P.y)     // a downward crossing
                if (isLeft(V[i], V[i + 1], P) < 0)  // 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 = 0;            // the  winding number counter
    int n = V.size() - 1;                    // loop through all edges of the polygon
    for (int i = 0; i<n; i++)
    {
        // edge from V[i] to  V[i+1]
        if (V[i].y <= P.y)
        {
            // start y <= P.y
            if (V[i + 1].y  > P.y)      // an upward crossing
                if (isLeft(V[i], V[i + 1], P) > 0)  // P left of  edge
                    ++wn;            // have  a valid up intersect
        }
        else
        {                        // start y > P.y (no test needed)
            if (V[i + 1].y <= P.y)     // a downward crossing
                if (isLeft(V[i], V[i + 1], P) < 0)  // 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[60];
    string filename;
    Point p2d;

    int length = sprintf(name, "%d%s", i + 1, "_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()<1)
            {
                continue;
            }
            else if (tokens.size() == 2)
            {
                int j = 0;
                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[0]);
        //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 = 2653; //1363, 1260   //2896,2276   //2653,390
    detectPoint.y = 390;
    std::string path="矫正后图像";

    std::vector<Point> pointVec;
    readImageROIpolygen(path, pointVec,0);
    if (pointVec.size()==0)
    {
        cout << "no ROI!!!" << endl;
        return;    
    }

    if (wn_PnPoly_ddb(detectPoint, pointVec) == 0)
    {
        cout << "detectPoint outside ImageROIpolygen!!!!" << endl;
    }
    else
    {
        cout << "detectPoint in ImageROIpolygen!!!!" << endl;
    }
    
    system("pause");
}