public void TrainRecognizer(List <User> users) { var imageList = new List <Mat>(); var indexList = new List <int>(); var userIndex = 0; foreach (var user in users) { foreach (var userImage in user.UserImages.Where(userImage => File.Exists(userImage.ImageFilePath))) { imageList.Add(new Mat(userImage.ImageFilePath).CvtColor(ColorConversionCodes.BGR2GRAY)); indexList.Add(userIndex); } userIndex++; } Recognizer = EigenFaceRecognizer.Create(); Recognizer.Train(imageList, indexList); }