How I can extract a face features as vector

edit

Hi pi-null-mezon! Thank you for your answer. I forgot to mention, that I don't have a training set for every people i.e. the face is found only once so I cannot use a classical approach to this problem (with using a training set and train Eigenface algorithm to recognize the face and extract the vector of internal state of the algorithm). Should I use FaceRecognizer class for this task and if so, what training set I can use? Thank you! P.S. http://stackoverflow.com/a/7030545 (Here) is something useful, but I'm not sure if it's correct to use some example database for training and then pass the mine face that I extracted previously to the algorithm only to get the vector and then use this vector to calculate some metrics algorithm.

Yes, you can use FaceRecognizer even in this case. As DB for feature space training you can use almost every open database. This is the one of the most popular megaface.