samples/cpp/camshiftdemo.cpp

An example using the mean-shift tracking algorithm

#include "opencv2/core/utility.hpp"
#include "opencv2/video/tracking.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/videoio.hpp"
#include "opencv2/highgui.hpp"
 
#include <iostream>
#include <ctype.h>
 
using namespace cv;
using namespace std;
 
Mat image;
 
bool backprojMode = false;
bool selectObject = false;
int trackObject = 0;
bool showHist = true;
Point origin;
Rect selection;
int vmin = 10, vmax = 256, smin = 30;
 
// User draws box around object to track. This triggers CAMShift to start tracking
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 EVENT_LBUTTONDOWN:
 origin = Point(x,y);
 selection = Rect(x,y,0,0);
 selectObject = true;
 break;
 case EVENT_LBUTTONUP:
 selectObject = false;
 if( selection.width > 0 && selection.height > 0 )
 trackObject = -1; // Set up CAMShift properties in main() loop
 break;
 }
}
 
string hot_keys =
 "\n\nHot keys: \n"
 "\tESC - quit the program\n"
 "\tc - stop the tracking\n"
 "\tb - switch to/from backprojection view\n"
 "\th - show/hide object histogram\n"
 "\tp - pause video\n"
 "To initialize tracking, select the object with mouse\n";
 
static void help(const char** argv)
{
 cout << "\nThis is a demo that shows mean-shift based tracking\n"
 "You select a color objects such as your face and it tracks it.\n"
 "This reads from video camera (0 by default, or the camera number the user enters\n"
 "Usage: \n\t";
 cout << argv[0] << " [camera number]\n";
 cout << hot_keys;
}
 
const char* keys =
{
 "{help h | | show help message}{@camera_number| 0 | camera number}"
};
 
int main( int argc, const char** argv )
{
 VideoCapture cap;
 Rect trackWindow;
 int hsize = 16;
 float hranges[] = {0,180};
 const float* phranges = hranges;
 CommandLineParser parser(argc, argv, keys);
 if (parser.has("help"))
 {
 help(argv);
 return 0;
 }
 int camNum = parser.get<int>(0);
 cap.open(camNum);
 
 if( !cap.isOpened() )
 {
 help(argv);
 cout << "***Could not initialize capturing...***\n";
 cout << "Current parameter's value: \n";
 parser.printMessage();
 return -1;
 }
 cout << hot_keys;
 namedWindow( "Histogram", 0 );
 namedWindow( "CamShift Demo", 0 );
 setMouseCallback( "CamShift Demo", onMouse, 0 );
 createTrackbar( "Vmin", "CamShift Demo", &vmin, 256, 0 );
 createTrackbar( "Vmax", "CamShift Demo", &vmax, 256, 0 );
 createTrackbar( "Smin", "CamShift Demo", &smin, 256, 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, COLOR_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 )
 {
 // Object has been selected by user, set up CAMShift search properties once
 Mat roi(hue, selection), maskroi(mask, selection);
 calcHist(&roi, 1, 0, maskroi, hist, 1, &hsize, &phranges);
 normalize(hist, hist, 0, 255, NORM_MINMAX);
 
 trackWindow = selection;
 trackObject = 1; // Don't set up again, unless user selects new ROI
 
 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, COLOR_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 );
 }
 }
 
 // Perform CAMShift
 calcBackProject(&hue, 1, 0, hist, backproj, &phranges);
 backproj &= mask;
 RotatedRect trackBox = CamShift(backproj, trackWindow,
 TermCriteria( TermCriteria::EPS | TermCriteria::COUNT, 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);
 }
 
 if( backprojMode )
 cvtColor( backproj, image, COLOR_GRAY2BGR );
 ellipse( image, trackBox, Scalar(0,0,255), 3, LINE_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 Demo", image );
 imshow( "Histogram", histimg );
 
 char c = (char)waitKey(10);
 if( c == 27 )
 break;
 switch(c)
 {
 case 'b':
 backprojMode = !backprojMode;
 break;
 case 'c':
 trackObject = 0;
 histimg = Scalar::all(0);
 break;
 case 'h':
 showHist = !showHist;
 if( !showHist )
 destroyWindow( "Histogram" );
 else
 namedWindow( "Histogram", 1 );
 break;
 case 'p':
 paused = !paused;
 break;
 default:
 ;
 }
 }
 
 return 0;
}