IMREAD PATH

edit

I'm trying to do a face detecction aplicattion with opencv, and I'm facing a problem with the path of the image that I want to pass as parameter, to test the face detecction. I don't know which directory I have to paste my image, and how can I read it, to pass to the imread. plus, do I need to ask any request like access to the external storage or something?

This is the code of the imread:

  System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
            try {

                File imgDir = getDir("imagens_teste", Context.MODE_PRIVATE);
                File cara = new File(imgDir, "cara.jpg");

                Mat imagemColorida = imread(cara.getAbsolutePath());
                Mat imagemCinza = new Mat();

I already tried this:

File root = Environment.getRootDirectory();
            File file = new File(root, "cara.jpg");


            Mat imagemColorida = imread(file.getAbsolutePath());
            Mat imagemCinza = new Mat();

and Mat imagemColorida = imread("src\\main\\imagens_teste\\cara.jpg");

can someone help me?