OpenCV: fit line (line-fitting )

// fit-line for 2-D data (line-fitting)
http://blog.weisu.org/2006/01/opencv-fit-line-line-fitting_14.html

#include "stdafx.h"
#include "cv.h"
#include "highgui.h"
#include <stdlib.h>

void main( int argc, char** argv )
{
     FILE *fp;
     int i;
     int count = 48;                     // total number of points
     int tmp1, tmp2;
     CvPoint  left, right;
     float *line;
     line = new float[4*count];
     IplImage* img=cvLoadImage("b.bmp",1);// just a black image
     cvNamedWindow( "input_image", CV_WINDOW_AUTOSIZE );

     fp = fopen("xy.txt", "r");          // xy.txt have the (x, y)
          position
     CvPoint* points = (CvPoint*)malloc( count * sizeof(points[0]));

     for (i=0; i<count; i++) {
             fscanf(fp, "%d %d", &tmp1, &tmp2);
             points[i].x = tmp1;
             points[i].y = tmp2;
             ((uchar*)(img->imageData + img->widthStep*tmp2))[tmp1*3 + 0]
              =255;
             ((uchar*)(img->imageData + img->widthStep*tmp2))[tmp1*3 + 1]
              =255;
             ((uchar*)(img->imageData + img->widthStep*tmp2))[tmp1*3 + 2]
              =255;
     }
     fclose(fp);
     cvShowImage("input_image", img);     // white spots with black
                 background
     cvWaitKey(0);

     CvMat point_mat = cvMat( 1, count, CV_32SC2, points );
     cvFitLine( &point_mat, CV_DIST_L2 , 0, // line[0]:vector_x, line[1]:
                vector_y
                0.01, 0.01,  line );        // line[2]:x_n, line[3]:y_n
     // we get the vector and one point
     // on the line, so the line is determined

     double a, b, c, d, e, f;               // y = a + b*x, b is slop
     b = line[1]/ line[0];                  // y = c + d*x
     a = line[3]- b*line[2];                // y = e + f*x
     d = -1/b;
     c = points[0].y - d*points[0].x;
     f = d;
     e = points[count-1].y - f*points[count-1].x;

     left.x = (a-c)/(d-b);                  // x = (a-c)/(d-b)
     left.y = c+d*left.x;                   // y = a + b*x
     right.x = (a-e)/(f-b);
     right.y = e+f*right.x;

     CvPoint center;
     center.x = line[2];
     center.y = line[3];
     // can draw from left to right directly
     cvLine( img, center, left, CV_RGB(255,0,0), 1, 8 );
     cvLine( img, center, right, CV_RGB(255,0,0), 1, 8 );
     cvShowImage("input_image", img);
     cvWaitKey(0);

     delete []line;
}

*** Line Fitting

http://kimhj8574.egloos.com/4734597

int count = 0;        // total number of points   
float 

*line;    
 
CvPoint  left, right;    

//CvMat point_mat = cvMat( 1, count, CV_32SC2, mid_points );    
//cvFitLine( &point_mat, CV_DIST_L2 , 0, // line[0]:vector_x, line[1]:vector_y               
// 0.01, 0.01,  line );        // line[2]:x_n, line[3]:y_n    
//
long double a, b, c, d, e, f;
////b가 기울기, a가 절편
//b = line[1]/ line[0];       
//a = line[3]- b*line[2];       
b=((float)right.y-(float)left.y)/((float)right.x-(float)right.y);

//left.x=mid_points[0].x;
//left.y=b*left.x+a;

//right.x=mid_points[count-1].x;
//right.y=b*right.x+a;

//CvPoint center;    
//center.x = line[2];    
//center.y = line[3];     // can draw from left to right directly    
//cvLine( processed_image, center, left, CV_RGB(255,255,255), 1, 8 );    
cvLine( Draw_results, left, right, CV_RGB(255,0,0), 1, 8 );