opencv/samples/cpp/watershed.cpp

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"

#include <cstdio>
#include <iostream>

using namespace cv;
using namespace std;

void help()
{
	cout << "\nThis program demonstrates the famous watershed segmentation algorithm in OpenCV: watershed()\n"
			"Usage:\n"
			"./watershed [image_name -- default is fruits.jpg]\n" << endl;


	cout << "Hot keys: \n"
		"\tESC - quit the program\n"
		"\tr - restore the original image\n"
		"\tw or SPACE - run watershed segmentation algorithm\n"
		"\t\t(before running it, *roughly* mark the areas to segment on the image)\n"
		"\t  (before that, roughly outline several markers on the image)\n";
}
Mat markerMask, img;
Point prevPt(-1, -1);

void onMouse( int event, int x, int y, int flags, void* )
{
    if( x < 0 || x >= img.cols || y < 0 || y >= img.rows )
        return;
    if( event == CV_EVENT_LBUTTONUP || !(flags & CV_EVENT_FLAG_LBUTTON) )
        prevPt = Point(-1,-1);
    else if( event == CV_EVENT_LBUTTONDOWN )
        prevPt = Point(x,y);
    else if( event == CV_EVENT_MOUSEMOVE && (flags & CV_EVENT_FLAG_LBUTTON) )
    {
        Point pt(x, y);
        if( prevPt.x < 0 )
            prevPt = pt;
        line( markerMask, prevPt, pt, Scalar::all(255), 5, 8, 0 );
        line( img, prevPt, pt, Scalar::all(255), 5, 8, 0 );
        prevPt = pt;
        imshow("image", img);
    }
}

int main( int argc, char** argv )
{
    char* filename = argc >= 2 ? argv[1] : (char*)"fruits.jpg";
    Mat img0 = imread(filename, 1), imgGray;
    
    if( img0.empty() )
    {
        cout << "Couldn'g open image " << filename << ". Usage: watershed <image_name>\n";
        return 0;
    }
    help();
    namedWindow( "image", 1 );

    img0.copyTo(img);
    cvtColor(img, markerMask, CV_BGR2GRAY);
    cvtColor(markerMask, imgGray, CV_GRAY2BGR);
    markerMask = Scalar::all(0);
    imshow( "image", img );
    setMouseCallback( "image", onMouse, 0 );

    for(;;)
    {
        int c = waitKey(0);

        if( (char)c == 27 )
            break;

        if( (char)c == 'r' )
        {
            markerMask = Scalar::all(0);
            img0.copyTo(img);
            imshow( "image", img );
        }

        if( (char)c == 'w' || (char)c == ' ' )
        {
            int i, j, compCount = 0;
            vector<vector<Point> > contours;
            vector<Vec4i> hierarchy;
            
            findContours(markerMask, contours, hierarchy, CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE);
            
            if( contours.empty() )
                continue;
            Mat markers(markerMask.size(), CV_32S);
            markers = Scalar::all(0);
            int idx = 0;
            for( ; idx >= 0; idx = hierarchy[idx][0], compCount++ )
                drawContours(markers, contours, idx, Scalar::all(compCount+1), -1, 8, hierarchy, INT_MAX);

            if( compCount == 0 )
                continue;
            
            vector<Vec3b> colorTab;
            for( i = 0; i < compCount; i++ )
            {
                int b = theRNG().uniform(0, 255);
                int g = theRNG().uniform(0, 255);
                int r = theRNG().uniform(0, 255);
                
                colorTab.push_back(Vec3b((uchar)b, (uchar)g, (uchar)r));
            }

            double t = (double)getTickCount();
            watershed( img0, markers );
            t = (double)getTickCount() - t;
            printf( "execution time = %gms\n", t*1000./getTickFrequency() );

            Mat wshed(markers.size(), CV_8UC3);
            
            // paint the watershed image
            for( i = 0; i < markers.rows; i++ )
                for( j = 0; j < markers.cols; j++ )
                {
                    int idx = markers.at<int>(i,j);
                    if( idx == -1 )
                        wshed.at<Vec3b>(i,j) = Vec3b(255,255,255);
                    else if( idx <= 0 || idx > compCount )
                        wshed.at<Vec3b>(i,j) = Vec3b(0,0,0);
                    else
                        wshed.at<Vec3b>(i,j) = colorTab[idx - 1];
                }

            wshed = wshed*0.5 + imgGray*0.5;
            imshow( "watershed transform", wshed );
        }
    }

    return 0;
}