#include <iostream>
#include "cv.h"
#include "highgui.h"
#include <math.h>
#define PI 3.14159265f
usingnamespacecv;

intmain()
{
intmax_r;          //Maximum magnitude of r
intmax_theta=179;  //Maximum value of theta.
int     threshold=60;   //Mimimum number of votes required by(theata,r) to form a straight line.
intimg_width;      //Width of the image
intimg_height;     //Height of the image
intnum_theta=180;  //Number of values of theta (0 - 179 degrees)
intnum_r;          //Number of values of r.
int     *accumulator;   //accumulator to collect votes.
longacc_size;       //size of the accumulator in bytes.
float   Sin[num_theta]; //Array to store pre-calculated vales of sin(theta)
float   Cos[num_theta]; //Array to store pre-calculated vales of cos(theta)
uchar   *img_data;      //pointer to image data for efficient access.
inti,j;
    Mat     src;
    Mat     dst;

    /*Read and Displaytheimage*/
    Mat image=imread("poly.png");
namedWindow("Polygon", 1 );
imshow("Polygon", image);
    //convert colortograyscaleimage
cvtColor(image, src, CV_BGR2GRAY);
    /*Initializations*/
img_width = src.cols;
img_height = src.rows;

//calculating maximum valueofr.Rounditofftonearestinteger.
max_r = round(sqrt( (img_width*img_width) + (img_height*img_height)));
        //calculating the numbervalesrcantake.-max_r<=r<=max_r
num_r = (max_r *2) +1;
        //pre-compute the valuesofsin(theta)andcos(theta).
for(i=0;i<=max_theta;i++)
        {
            Sin[i] = sin(i * (PI/180));
            Cos[i] = cos(i * (PI/180));
        }
        //Initializing the accumulator.Conceptuallyitisa2-Dmatrixwithdimensionrxtheta
accumulator = new int[num_theta * num_r];
//calculating size ofaccumulatorinbytes.
acc_size = sizeof(int)*num_theta * num_r;
//Initializing elements ofaccumulatortozero.
memset(accumulator,0,acc_size);
//extracting the edges.
Canny(src,dst,50,200,3);

    //Getting the imagedatafromMatdst
img_data = dst.data;
//Loop through allthepixels.Eachpixelisrepresentedby1byte.
for(i=0;i<img_height;i++)
    {
for(j=0;j<img_width;j++)
        {
            //Getting the pixel value.
intval =img_data[i*img_width+j];

if(val>0)
            {
                //if pixel is notblackdothefollowing.
                //For that pixelfindthethevaluesofrforcorrespondingvalueoftheta.
                //Value of rcanbenegative.(See the graph)
                //Minimum value ofris-max_r.
                //Conceptually the arraylookslikethis
                //          0  1  2  3  4  5  6  .. 178  179<---degrees
                // -max_r  |  |  |  |  |  |  |  |  |    |   |
                // -max_r+1|  |  |  |  |  |  |  |  |    |   |
                // -max_r+2|  |  |  |  |  |  |  |  |    |   |
                //   ...   |  |  |  |  |  |  |  |  |    |   |
                //    0    |  |  |  |  |  |  |  |  |    |   |
                //    1    |  |  |  |  |  |  |  |  |    |   |
                //    2    |  |  |  |  |  |  |  |  |    |   |
                //   ...   |  |  |  |  |  |  |  |  |    |   |
                //   max_r|  |  |  |  |  |  |  |  |    |   |
                //
for(int t=0;t<=max_theta;t++)
                {
                    //calculating the values of r for theta= t , x= j and y=i;
int_r=round(j*Cos[t] + i*Sin[t]);
                    //calculating the rowindexof_rintheaccumulator.
intr_index=(max_r+_r);
                    //Registering the votebyincrementingthevalueofaccumulator[r][theta]
accumulator[r_index*num_theta + t]++;

                }

            }
        }
    }

    //Looping through eachelementintheaccumulator
for(intr_index=0;r_index<num_r;r_index++)
    {
for(j=0;j<num_theta;j++)
        {
//retrieve the votes.
int votes = accumulator[r_index*num_theta+j];
if(votes>threshold)
            {
                //if votes receive isgreaterthanthethreshold

                //getting the valueoftheta
int_theta=j;
                //getting the valueofr
int_r=r_index-max_r;

                //Calculating points todrawtheline.
                Point pt1, pt2;
                pt1.x =0;
                pt1.y =round((_r - pt1.x*Cos[_theta])/Sin[_theta]);
                pt2.x =img_width;
                pt2.y =round((_r - pt2.x*Cos[_theta])/Sin[_theta]);
                //Drawing the line.
line( image, pt1, pt2, Scalar(0,255,0), 3, CV_AA);
            }

        }
    }
namedWindow("Detected Lines", 1 );
imshow("Detected Lines",image);
    //Free the memoryallocatedtoaccumulator.
delete[] accumulator;
waitKey(0);

return 0;
}