main.cpp

// Tracks the selected object using CAMShift algorithm

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

#include <iostream>
#include <ctype.h>

using namespace cv;
using namespace std;

Mat image;

bool selectObject = false;
int trackObject = 0;
Point origin;
Rect selection;
int vmin = 10, vmax = 256, smin = 30;

static void onMouse( int event, int x, int y, int, void* )
{
    if( selectObject )
    {
        selection.x = MIN(x, origin.x);
        selection.y = MIN(y, origin.y);
        selection.width = std::abs(x - origin.x);
        selection.height = std::abs(y - origin.y);
        
        selection &= Rect(0, 0, image.cols, image.rows);
    }
    
    switch( event )
    {
        case CV_EVENT_LBUTTONDOWN:
            origin = Point(x,y);
            selection = Rect(x,y,0,0);
            selectObject = true;
            break;
        case CV_EVENT_LBUTTONUP:
            selectObject = false;
            if( selection.width > 0 && selection.height > 0 )
                trackObject = -1;
            break;
    }
}

static void help()
{
    cout << "\nCAMShift based object tracking\n"
    "You select a colored object and the algorithm tracks it.\n"
    "This takes the input from the webcam\n"
    "Usage: \n"
    "$ ./main [camera number]\n";
    
    cout << "\n\nKeyboard input options: \n"
    "\tESC - quit the program\n"
    "\ts - stop the tracking\n"
    "\tp - pause video\n"
    "\nTo start tracking an object, select the rectangular region around it with the mouse\n\n";
}

int main( int argc, const char** argv )
{
    help();
    
    VideoCapture cap;
    Rect trackWindow;
    int hsize = 16;
    float hranges[] = {0,180};
    const float* phranges = hranges;
    
    int camNum = 0;
    if(argc == 2)
        camNum = atoi(argv[1]);
    
    cap.open(camNum);
    
    if( !cap.isOpened() )
    {
        help();
        cout << "***Could not initialize capturing...***\n";
        cout << "Current parameter's value: " << camNum << endl;
        return -1;
    }
    
    namedWindow( "CamShift Object Tracker", 0 );
    setMouseCallback( "CamShift Object Tracker", onMouse, 0 );
    
    Mat frame, hsv, hue, mask, hist, histimg = Mat::zeros(200, 320, CV_8UC3), backproj;
    bool paused = false;
    
    for(;;)
    {
        if( !paused )
        {
            cap >> frame;
            if( frame.empty() )
                break;
        }
        
        frame.copyTo(image);
        
        if( !paused )
        {
            cvtColor(image, hsv, CV_BGR2HSV);
            
            if( trackObject )
            {
                int _vmin = vmin, _vmax = vmax;
                
                inRange(hsv, Scalar(0, smin, MIN(_vmin,_vmax)),
                        Scalar(180, 256, MAX(_vmin, _vmax)), mask);
                int ch[] = {0, 0};
                hue.create(hsv.size(), hsv.depth());
                mixChannels(&hsv, 1, &hue, 1, ch, 1);
                
                if( trackObject < 0 )
                {
                    Mat roi(hue, selection), maskroi(mask, selection);
                    calcHist(&roi, 1, 0, maskroi, hist, 1, &hsize, &phranges);
                    normalize(hist, hist, 0, 255, CV_MINMAX);
                    
                    trackWindow = selection;
                    trackObject = 1;
                    
                    histimg = Scalar::all(0);
                    int binW = histimg.cols / hsize;
                    Mat buf(1, hsize, CV_8UC3);
                    for( int i = 0; i < hsize; i++ )
                        buf.at<Vec3b>(i) = Vec3b(saturate_cast<uchar>(i*180./hsize), 255, 255);
                    cvtColor(buf, buf, CV_HSV2BGR);
                    
                    for( int i = 0; i < hsize; i++ )
                    {
                        int val = saturate_cast<int>(hist.at<float>(i)*histimg.rows/255);
                        rectangle( histimg, Point(i*binW,histimg.rows),
                                  Point((i+1)*binW,histimg.rows - val),
                                  Scalar(buf.at<Vec3b>(i)), -1, 8 );
                    }
                }
                
                calcBackProject(&hue, 1, 0, hist, backproj, &phranges);
                backproj &= mask;
                RotatedRect trackBox = CamShift(backproj, trackWindow,
                                                TermCriteria( CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 10, 1 ));
                if( trackWindow.area() <= 1 )
                {
                    int cols = backproj.cols, rows = backproj.rows, r = (MIN(cols, rows) + 5)/6;
                    trackWindow = Rect(trackWindow.x - r, trackWindow.y - r,
                                       trackWindow.x + r, trackWindow.y + r) &
                    Rect(0, 0, cols, rows);
                }
                
                ellipse( image, trackBox, Scalar(0,0,255), 3, CV_AA );
            }
        }
        else if( trackObject < 0 )
            paused = false;
        
        if( selectObject && selection.width > 0 && selection.height > 0 )
        {
            Mat roi(image, selection);
            bitwise_not(roi, roi);
        }
        
        imshow( "CamShift Object Tracker", image );
        
        char c = (char)waitKey(10);
        if( c == 27 )
            break;
        switch(c)
        {
            case 's':
                trackObject = 0;
                histimg = Scalar::all(0);
                break;

            case 'p':
                paused = !paused;
                break;
                
            default:
                ;
        }
    }
    
    return 0;
}