opencv in java use MAT instead of vector for labels

Question

In the FaceRecognition class from java jni I have the following train method:

public  void train(List<Mat> src, Mat labels)

In all the examples "labels" is a vector, not a Mat. In the c++ documentation I did found:

The labels of each image are stored within a std::vector<int> (you could also use a Mat of type CV_32SC1).

but I'm not sure how to do this in java. How do I construct a Mat of type CV_32SC1 that contains a list of int?

Answer 1

I was able to figure it out in the end:

List<Mat> src = new ArrayList<>();

Mat image = Highgui.imread("faces/s1/1.pgm", 0);
src.add(image);

image = Highgui.imread("faces/s1/2.pgm", 0);
src.add(image);

image = Highgui.imread("faces/s1/3.pgm", 0);
src.add(image);

image = Highgui.imread("faces/s1/4.pgm", 0);
src.add(image); 

image = Highgui.imread("faces/s2/1.pgm", 0);
src.add(image);

image = Highgui.imread("faces/s2/2.pgm", 0);
src.add(image);

image = Highgui.imread("faces/s2/3.pgm", 0);
src.add(image);

image = Highgui.imread("faces/s2/4.pgm", 0);
src.add(image);   

Mat labels = new Mat(8, 1, CvType.CV_32SC1);
labels.put(0, 0, 1);
labels.put(1, 0, 1);
labels.put(2, 0, 1);
labels.put(3, 0, 1);
labels.put(4, 0, 2);
labels.put(5, 0, 2);
labels.put(6, 0, 2);
labels.put(7, 0, 2);

FaceRecognizer recognizer = new LBPHFaceRecognizer();
recognizer.train(src, labels);