fitellipse.cpp

An example using the fitEllipse technique

/********************************************************************************
*
*
* 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.
*
*
*
********************************************************************************/
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <iostream>
using namespace cv;
using namespace std;

// static void help()
// {
// cout <<
// "\nThis program is demonstration for ellipse fitting. The program finds\n"
// "contours and approximate it by ellipses.\n"
// "Call:\n"
// "./fitellipse [image_name -- Default ../data/stuff.jpg]\n" << endl;
// }

int sliderPos = 70;

Mat image;

void processImage(int, void*);

int main( int argc, char** argv )
{
 const char* filename = argc == 2 ? argv[1] : (char*)"../data/stuff.jpg";
 image = imread(filename, 0);
 if( image.empty() )
 {
 cout << "Couldn't open image " << filename << "\nUsage: fitellipse <image_name>\n";
 return 0;
 }

 imshow("source", image);
 namedWindow("result", 1);

 // Create toolbars. HighGUI use.
 createTrackbar( "threshold", "result", &sliderPos, 255, processImage );
 processImage(0, 0);

 // Wait for a key stroke; the same function arranges events processing
 waitKey();
 return 0;
}

// Define trackbar callback functon. This function find contours,
// draw it and approximate it by ellipses.
void processImage(int /*h*/, void*)
{
 vector<vector<Point> > contours;
 Mat bimage = image >= sliderPos;

 findContours(bimage, contours, RETR_LIST, CHAIN_APPROX_NONE);

 Mat cimage = Mat::zeros(bimage.size(), CV_8UC3);

 for(size_t i = 0; i < contours.size(); i++)
 {
 size_t count = contours[i].size();
 if( count < 6 )
 continue;

 Mat pointsf;
 Mat(contours[i]).convertTo(pointsf, CV_32F);
 RotatedRect box = fitEllipse(pointsf);

 if( MAX(box.size.width, box.size.height) > MIN(box.size.width, box.size.height)*30 )
 continue;
 drawContours(cimage, contours, (int)i, Scalar::all(255), 1, 8);

 ellipse(cimage, box, Scalar(0,0,255), 1, LINE_AA);
 ellipse(cimage, box.center, box.size*0.5f, box.angle, 0, 360, Scalar(0,255,255), 1, LINE_AA);
 Point2f vtx[4];
 box.points(vtx);
 for( int j = 0; j < 4; j++ )
 line(cimage, vtx[j], vtx[(j+1)%4], Scalar(0,255,0), 1, LINE_AA);
 }

 imshow("result", cimage);
}