2 Tracking of rotating point.
3 Rotation speed is constant.
4 Both state and measurements vectors are 1D (a point angle),
5 Measurement is the real point angle + gaussian noise.
6 The real and the estimated points are connected with yellow line segment,
7 the real and the measured points are connected with red line segment.
8 (if Kalman filter works correctly,
9 the yellow segment should be shorter than the red one).
10 Pressing any key (except ESC) will reset the tracking with a different speed.
11 Pressing ESC will stop the program.
14 #include "opencv2/video/tracking.hpp"
15 #include "opencv2/highgui/highgui.hpp"
17 int main(int argc, char** argv)
19 const float A[] = { 1, 1, 0, 1 };
21 IplImage* img = cvCreateImage( cvSize(500,500), 8, 3 );
22 CvKalman* kalman = cvCreateKalman( 2, 1, 0 );
23 CvMat* state = cvCreateMat( 2, 1, CV_32FC1 ); /* (phi, delta_phi) */
24 CvMat* process_noise = cvCreateMat( 2, 1, CV_32FC1 );
25 CvMat* measurement = cvCreateMat( 1, 1, CV_32FC1 );
26 CvRNG rng = cvRNG(-1);
29 cvZero( measurement );
30 cvNamedWindow( "Kalman", 1 );
34 cvRandArr( &rng, state, CV_RAND_NORMAL, cvRealScalar(0), cvRealScalar(0.1) );
36 memcpy( kalman->transition_matrix->data.fl, A, sizeof(A));
37 cvSetIdentity( kalman->measurement_matrix, cvRealScalar(1) );
38 cvSetIdentity( kalman->process_noise_cov, cvRealScalar(1e-5) );
39 cvSetIdentity( kalman->measurement_noise_cov, cvRealScalar(1e-1) );
40 cvSetIdentity( kalman->error_cov_post, cvRealScalar(1));
41 cvRandArr( &rng, kalman->state_post, CV_RAND_NORMAL, cvRealScalar(0), cvRealScalar(0.1) );
45 #define calc_point(angle) \
46 cvPoint( cvRound(img->width/2 + img->width/3*cos(angle)), \
47 cvRound(img->height/2 - img->width/3*sin(angle)))
49 float state_angle = state->data.fl[0];
50 CvPoint state_pt = calc_point(state_angle);
52 const CvMat* prediction = cvKalmanPredict( kalman, 0 );
53 float predict_angle = prediction->data.fl[0];
54 CvPoint predict_pt = calc_point(predict_angle);
55 float measurement_angle;
56 CvPoint measurement_pt;
58 cvRandArr( &rng, measurement, CV_RAND_NORMAL, cvRealScalar(0),
59 cvRealScalar(sqrt(kalman->measurement_noise_cov->data.fl[0])) );
61 /* generate measurement */
62 cvMatMulAdd( kalman->measurement_matrix, state, measurement, measurement );
64 measurement_angle = measurement->data.fl[0];
65 measurement_pt = calc_point(measurement_angle);
68 #define draw_cross( center, color, d ) \
69 cvLine( img, cvPoint( center.x - d, center.y - d ), \
70 cvPoint( center.x + d, center.y + d ), color, 1, CV_AA, 0); \
71 cvLine( img, cvPoint( center.x + d, center.y - d ), \
72 cvPoint( center.x - d, center.y + d ), color, 1, CV_AA, 0 )
75 draw_cross( state_pt, CV_RGB(255,255,255), 3 );
76 draw_cross( measurement_pt, CV_RGB(255,0,0), 3 );
77 draw_cross( predict_pt, CV_RGB(0,255,0), 3 );
78 cvLine( img, state_pt, measurement_pt, CV_RGB(255,0,0), 3, CV_AA, 0 );
79 cvLine( img, state_pt, predict_pt, CV_RGB(255,255,0), 3, CV_AA, 0 );
81 cvKalmanCorrect( kalman, measurement );
83 cvRandArr( &rng, process_noise, CV_RAND_NORMAL, cvRealScalar(0),
84 cvRealScalar(sqrt(kalman->process_noise_cov->data.fl[0])));
85 cvMatMulAdd( kalman->transition_matrix, state, process_noise, state );
87 cvShowImage( "Kalman", img );
88 code = (char) cvWaitKey( 100 );
93 if( code == 27 || code == 'q' || code == 'Q' )
97 cvDestroyWindow("Kalman");