opencv/samples/python2/gaussian_mix.py

import numpy as np
from numpy import random
import cv2

def make_gaussians(cluster_n, img_size):
    points = []
    ref_distrs = []
    for i in xrange(cluster_n):
        mean = (0.1 + 0.8*random.rand(2)) * img_size
        a = (random.rand(2, 2)-0.5)*img_size*0.1
        cov = np.dot(a.T, a) + img_size*0.05*np.eye(2)
        n = 100 + random.randint(900)
        pts = random.multivariate_normal(mean, cov, n)
        points.append( pts )
        ref_distrs.append( (mean, cov) )
    points = np.float32( np.vstack(points) )
    return points, ref_distrs

def draw_gaussain(img, mean, cov, color):
    x, y = np.int32(mean)
    w, u, vt = cv2.SVDecomp(cov)
    ang = np.arctan2(u[1, 0], u[0, 0])*(180/np.pi)
    s1, s2 = np.sqrt(w)*3.0
    cv2.ellipse(img, (x, y), (s1, s2), ang, 0, 360, color, 1, cv2.CV_AA)


if __name__ == '__main__':
    cluster_n = 5
    img_size = 512

    print 'press any key to update distributions, ESC - exit\n'

    while True:
        print 'sampling distributions...'
        points, ref_distrs = make_gaussians(cluster_n, img_size)

        print 'EM (opencv) ...'
        em = cv2.EM(cluster_n, cv2.EM_COV_MAT_GENERIC)
        em.train(points)
        means = em.getMat('means')
        covs = em.getMatVector('covs')
        found_distrs = zip(means, covs)
        print 'ready!\n'

        img = np.zeros((img_size, img_size, 3), np.uint8)
        for x, y in np.int32(points):
            cv2.circle(img, (x, y), 1, (255, 255, 255), -1)
        for m, cov in ref_distrs:
            draw_gaussain(img, m, cov, (0, 255, 0))
        for m, cov in found_distrs:
            draw_gaussain(img, m, cov, (0, 0, 255))

        cv2.imshow('gaussian mixture', img)
        ch = 0xFF & cv2.waitKey(0)
        if ch == 27:
            break
    cv2.destroyAllWindows()