3 Tracking of rotating point.
4 Rotation speed is constant.
5 Both state and measurements vectors are 1D (a point angle),
6 Measurement is the real point angle + gaussian noise.
7 The real and the estimated points are connected with yellow line segment,
8 the real and the measured points are connected with red line segment.
9 (if Kalman filter works correctly,
10 the yellow segment should be shorter than the red one).
11 Pressing any key (except ESC) will reset the tracking with a different speed.
12 Pressing ESC will stop the program.
14 from opencv.cv import *
15 from opencv.highgui import *
16 from math import cos, sin, sqrt
18 if __name__ == "__main__":
19 A = [ [1, 1], [0, 1] ];
21 img = cvCreateImage( cvSize(500,500), 8, 3 );
22 kalman = cvCreateKalman( 2, 1, 0 );
23 state = cvCreateMat( 2, 1, CV_32FC1 ); # (phi, delta_phi)
24 process_noise = cvCreateMat( 2, 1, CV_32FC1 );
25 measurement = cvCreateMat( 1, 1, CV_32FC1 );
29 cvZero( measurement );
30 cvNamedWindow( "Kalman", 1 );
33 cvRandArr( rng, state, CV_RAND_NORMAL, cvRealScalar(0), cvRealScalar(0.1) );
35 kalman.transition_matrix[:] = A;
36 cvSetIdentity( kalman.measurement_matrix, cvRealScalar(1) );
37 cvSetIdentity( kalman.process_noise_cov, cvRealScalar(1e-5) );
38 cvSetIdentity( kalman.measurement_noise_cov, cvRealScalar(1e-1) );
39 cvSetIdentity( kalman.error_cov_post, cvRealScalar(1));
40 cvRandArr( rng, kalman.state_post, CV_RAND_NORMAL, cvRealScalar(0), cvRealScalar(0.1) );
43 def calc_point(angle):
44 return cvPoint( cvRound(img.width/2 + img.width/3*cos(angle)),
45 cvRound(img.height/2 - img.width/3*sin(angle)))
47 state_angle = state[0]
48 state_pt = calc_point(state_angle);
50 prediction = cvKalmanPredict( kalman );
51 predict_angle = prediction[0,0]
52 predict_pt = calc_point(predict_angle);
54 cvRandArr( rng, measurement, CV_RAND_NORMAL, cvRealScalar(0),
55 cvRealScalar(sqrt(kalman.measurement_noise_cov[0,0])) );
57 # generate measurement
58 cvMatMulAdd( kalman.measurement_matrix, state, measurement, measurement );
60 measurement_angle = measurement[0,0];
61 measurement_pt = calc_point(measurement_angle);
64 def draw_cross( center, color, d ):
65 cvLine( img, cvPoint( center.x - d, center.y - d ),
66 cvPoint( center.x + d, center.y + d ), color, 1, CV_AA, 0);
67 cvLine( img, cvPoint( center.x + d, center.y - d ),
68 cvPoint( center.x - d, center.y + d ), color, 1, CV_AA, 0 )
71 draw_cross( state_pt, CV_RGB(255,255,255), 3 );
72 draw_cross( measurement_pt, CV_RGB(255,0,0), 3 );
73 draw_cross( predict_pt, CV_RGB(0,255,0), 3 );
74 cvLine( img, state_pt, measurement_pt, CV_RGB(255,0,0), 3, CV_AA, 0 );
75 cvLine( img, state_pt, predict_pt, CV_RGB(255,255,0), 3, CV_AA, 0 );
77 cvKalmanCorrect( kalman, measurement );
79 cvRandArr( rng, process_noise, CV_RAND_NORMAL, cvRealScalar(0),
80 cvRealScalar(sqrt(kalman.process_noise_cov[0,0])));
81 cvMatMulAdd( kalman.transition_matrix, state, process_noise, state );
83 cvShowImage( "Kalman", img );
84 code = cvWaitKey( 100 );
89 if( code == '\x1b' or code == 'q' or code == 'Q' ):
92 cvDestroyWindow("Kalman");