opencv/samples/cpp/convexhull.cpp

#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <fstream>
#include <iostream>

using namespace cv;
using namespace std;

void help()
{
	cout << "\nThis sample demonstrates the use of the convexHull() function\n"
		 << "Call:\n"
		 << "./convexhull\n" << endl;
}

int main( int argc, char** argv )
{
    Mat img(500, 500, CV_8UC3);
    RNG& rng = theRNG();

    help();

    for(;;)
    {
        char key;
        int i, count = (unsigned)rng%100 + 1;
        
        vector<Point> points;

        for( i = 0; i < count; i++ )
        {
            Point pt;
            pt.x = rng.uniform(img.cols/4, img.cols*3/4);
            pt.y = rng.uniform(img.rows/4, img.rows*3/4);
            
            points.push_back(pt);
        }
        
        vector<int> hull;
        convexHull(Mat(points), hull, CV_CLOCKWISE);
        
        img = Scalar::all(0);
        for( i = 0; i < count; i++ )
            circle(img, points[i], 3, Scalar(0, 0, 255), CV_FILLED, CV_AA);
        
        int hullcount = (int)hull.size();
        Point pt0 = points[hull[hullcount-1]];
        
        for( i = 0; i < hullcount; i++ )
        {
            Point pt = points[hull[i]];
            line(img, pt0, pt, Scalar(0, 255, 0), 1, CV_AA);
            pt0 = pt;
        }

        imshow("hull", img);

        key = (char)waitKey();
        if( key == 27 || key == 'q' || key == 'Q' ) // 'ESC'
            break;
    }

    return 0;
}