/examples/opencv/src/fitellipse.cpp

/********************************************************************************
*
*
*  This program is demonstration for ellipse fitting. Program finds
*  contours and approximate it by ellipses.
*
*  Trackbar specify threshold parametr.
*
*  White lines is contours. Red lines is fitting ellipses.
*
*
*  Autor:  Denis Burenkov.
*
*
*
********************************************************************************/
#ifdef _CH_
#pragma package <opencv>
#endif

#define CV_NO_BACKWARD_COMPATIBILITY

#ifndef _EiC
#include "cv.h"
#include "highgui.h"
#endif

int slider_pos = 70;

// Load the source image. HighGUI use.
IplImage *image02 = 0, *image03 = 0, *image04 = 0;

void process_image(int h);

int main( int argc, char** argv )
{
    const char* filename = argc == 2 ? argv[1] : (char*)"stuff.jpg";

    // load image and force it to be grayscale
    if( (image03 = cvLoadImage(filename, 0)) == 0 )
        return -1;

    // Create the destination images
    image02 = cvCloneImage( image03 );
    image04 = cvCloneImage( image03 );

    // Create windows.
    cvNamedWindow("Source", 1);
    cvNamedWindow("Result", 1);

    // Show the image.
    cvShowImage("Source", image03);

    // Create toolbars. HighGUI use.
    cvCreateTrackbar( "Threshold", "Result", &slider_pos, 255, process_image );

    process_image(0);

    // Wait for a key stroke; the same function arranges events processing
    cvWaitKey(0);
    cvReleaseImage(&image02);
    cvReleaseImage(&image03);

    cvDestroyWindow("Source");
    cvDestroyWindow("Result");

    return 0;
}

// Define trackbar callback functon. This function find contours,
// draw it and approximate it by ellipses.
void process_image(int h)
{
    CvMemStorage* storage;
    CvSeq* contour;

    // Create dynamic structure and sequence.
    storage = cvCreateMemStorage(0);
    contour = cvCreateSeq(CV_SEQ_ELTYPE_POINT, sizeof(CvSeq), sizeof(CvPoint) , storage);

    // Threshold the source image. This needful for cvFindContours().
    cvThreshold( image03, image02, slider_pos, 255, CV_THRESH_BINARY );

    // Find all contours.
    cvFindContours( image02, storage, &contour, sizeof(CvContour),
                    CV_RETR_LIST, CV_CHAIN_APPROX_NONE, cvPoint(0,0));

    // Clear images. IPL use.
    cvZero(image02);
    cvZero(image04);

    // This cycle draw all contours and approximate it by ellipses.
    for(;contour;contour = contour->h_next)
    {
        int count = contour->total; // This is number point in contour
        CvPoint center;
        CvSize size;
        CvBox2D box;

        // Number point must be more than or equal to 6 (for cvFitEllipse_32f).
        if( count < 6 )
            continue;

        CvMat* points_f = cvCreateMat( 1, count, CV_32FC2 );
        CvMat points_i = cvMat( 1, count, CV_32SC2, points_f->data.ptr );
        cvCvtSeqToArray( contour, points_f->data.ptr, CV_WHOLE_SEQ );
        cvConvert( &points_i, points_f );

        // Fits ellipse to current contour.
        box = cvFitEllipse2( points_f );

        // Draw current contour.
        cvDrawContours(image04,contour,CV_RGB(255,255,255),CV_RGB(255,255,255),0,1,8,cvPoint(0,0));

        // Convert ellipse data from float to integer representation.
        center = cvPointFrom32f(box.center);
        size.width = cvRound(box.size.width*0.5);
        size.height = cvRound(box.size.height*0.5);

        // Draw ellipse.
        cvEllipse(image04, center, size,
                  -box.angle, 0, 360,
                  CV_RGB(0,0,255), 1, CV_AA, 0);

        cvReleaseMat(&points_f);
    }

    // Show image. HighGUI use.
    cvShowImage( "Result", image04 );
}

#ifdef _EiC
main(1,"fitellipse.c");
#endif