2015-07-25 07:54:23 -0500 commented answer opencv3 EM.getCovs(covs) you're the man. Thank you 2015-07-24 13:40:37 -0500 asked a question opencv3 EM.getCovs(covs) what type should covs be in getCovs(covs)? From the 3.0-beta c++, "Returns vector std::vector& covs of covariation matrices. Number of matrices is the number of gaussian mixtures, each matrix is a square floating-point matrix NxN, where N is the space dimensionality." from this old opencv2 bug, I understand that "vector corresponds to a list of numpy arrays, not 3D numpy array (since matrices in vector can in general have different size.) " from cv2 import ml import numpy as np def dictionary(descriptors, number_clusters=N): covs = [np.zeros(( N, N), np.float64)] em = ml.EM_create() em.setClustersNumber(N) em.trainEM(descriptors) means = em.getMeans() covs = em.getCovs(covs) weights = em.getWeights() return np.float32(means), np.float32(covs), np.float32(weights)[0]  printing out covs just prints out the original [np.zeros(( N, N), np.float64)]. Any body know how to get the covs? Note that attempting to run this code will not work without fixing this bug and rebuilding. 2015-07-24 08:12:33 -0500 received badge ● Supporter (source) 2015-07-23 13:22:54 -0500 commented answer How to get luminosity from the camera Android ? luminance = luminosity / m.squared. So the asker just needs to multiply the luminance value by the area being photographed? or the area of the lens? please explain @Lorena GdL instead of just telling me that I'm wrong 2015-07-23 12:54:04 -0500 commented answer How to get luminosity from the camera Android ? that was a typo; fixed 2015-07-23 12:47:46 -0500 commented answer opencv3 Expectation Maximization Python getCovs plea acknowledged and accepted. I will definitely start contributing... 2015-07-23 11:46:30 -0500 commented answer opencv3 Expectation Maximization Python getCovs got it. thanks 4 your help. 2015-07-23 11:23:22 -0500 commented answer opencv3 Expectation Maximization Python getCovs yes it is opencv3. Once fixed, will I need to rebuild opencv from scratch? 2015-07-23 11:21:32 -0500 received badge ● Scholar (source) 2015-07-23 11:21:30 -0500 commented answer opencv3 Expectation Maximization Python getCovs haha i see. please do make the pr if u don't mind 2015-07-23 11:18:44 -0500 received badge ● Editor (source) 2015-07-23 11:16:41 -0500 commented answer How to get luminosity from the camera Android ? @thdrksdfthmn interesting. thanks...I've removed that portion of the answer 2015-07-23 10:40:11 -0500 received badge ● Student (source) 2015-07-23 10:07:18 -0500 asked a question opencv3 Expectation Maximization Python getCovs How do I use the em.getCovs() function in python with opencv3? def dictionary(descriptors, N): em = cv2.ml.EM_create() em.setClustersNumber(N) em.trainEM(descriptors) means = em.getMeans() covs = em.getCovs() weights = em.getWeights() return np.float32(means), np.float32(covs), np.float32(weights)  I keep getting a AttributeError: 'cv2.ml_EM' object has no attribute 'getCovs' 2015-07-23 10:07:18 -0500 answered a question How to get luminosity from the camera Android ? I don't have any android experience, but you can easily calculate luminosity like so... 1) Splitting image into R, G, B values, something like b, g, r = cv2.split(img) 2) Average the b, g, r values over the entire image --> b_avg = average(b) 3) compute luminosity w/ the following equation: double luminosity = r_avg*0.299 + g_avg*0.587 + b_avg*0.114 from this tutorial: "The reason these values are weighted is because pure red, green and blue are actually darker/lighter than each other, with green being the darkest and blue being the lightest."