pihmLIBS/simplifyPolyline.h

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#include <iostream>
#include <math.h>

using namespace std;

struct Point{
        double x, y;
};

double dPointToLine(Point L1, Point L2, Point P){
        double dist; 
        dist = (L1.y-L2.y)*P.x + (L2.x-L1.x)*P.y + (L1.x*L2.y - L2.x*L1.y);
        dist = dist / sqrt(pow((L2.x-L1.x),2) + pow((L2.y-L1.y),2));
        if(L1.x==L2.x && L1.y==L2.y)
                dist = sqrt(pow((L1.x-P.x),2) + pow((L1.y-P.y),2));
        return (dist>0?dist:(-dist));
}
/*
void simplify_Polyline(Point *poly, int start, int end, double tolerance, int *marker, int flag){ //
        // Flag accounts if the function is called for the first time.. 0=>first time; 1=>otherwise
        if (end < start+1)
                return;
        cout<<start<<"\t"<<end<<"\n";
        static int count=0;
        if(flag == 0)
                count = 0;
        int     maxIndex = start;      // index of vertex farthest from S
        double   maxDistance = 0;       // distance squared of farthest vertex
    
        for (int i=start+1; i<end; i++){
                double dist = dPointToLine(poly[start], poly[end], poly[i]);
                if(dist > maxDistance){
                        maxDistance = dist;
                        maxIndex = i;
                }
        }

        if(maxDistance>tolerance){
                marker[count] = maxIndex;
                cout<<"count= "<<count<<"\n";
                cout<<"marker="<<marker[count]<<"\n";
                count++;
                simplify_Polyline(poly, start, maxIndex, tolerance, marker, 1);
                simplify_Polyline(poly, maxIndex, end, tolerance, marker, 1);
        }
        return;
}
*/
void simplifyPolyline(Point *poly, int start, int end, double tolerance, int *marker){ //, int flag){ //
        // Flag accounts if the function is called for the first time.. 0=>first time; 1=>otherwise
        if (end < start+1)
                return;// 0;
        //cout<<start<<"\t"<<end<<"\n";
        /*static int count=1;
        if(flag == 0)
                count = 1; */
        int     maxIndex = start;      // index of vertex farthest from S
        double   maxDistance = 0;       // distance squared of farthest vertex
    
        for (int i=start+1; i<end; i++){
                double dist = dPointToLine(poly[start], poly[end], poly[i]);
                if(dist > maxDistance){
                        maxDistance = dist;
                        maxIndex = i;
                }
        }

        if(maxDistance>tolerance){
                //marker[count] = maxIndex;
                marker[maxIndex]=1;
                //cout<<"count= "<<count<<"\n";
                //cout<<"marker="<<marker[count]<<"\n";
                //count++;
                simplifyPolyline(poly, start, maxIndex, tolerance, marker);
                simplifyPolyline(poly, maxIndex, end, tolerance, marker);
        }
        return;// count;
}
        

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