Reading an image from drawable folder- android

edit

I have my image file under drawable folder, I am trying to read the image to process it further.This is the method I am using ,image.width() always return 0,I am not getting any errors in the log cat.

    public Mat loadImageFromFile(String fileName) {

    Mat rgbLoadedImage = null;

    File root = Environment.getExternalStorageDirectory();
    File file = new File(root, fileName);

    // this should be in BGR format according to the
    // documentation.
    Mat image = Highgui.imread(file.getAbsolutePath());

    if (image.width() > 0) {

        rgbLoadedImage = new Mat(image.size(), image.type());

        Imgproc.cvtColor(image, rgbLoadedImage, Imgproc.COLOR_BGR2RGB);

        if (DEBUG)
            Log.d(TAG, "loadedImage: " + "chans: " + image.channels()
                    + ", (" + image.width() + ", " + image.height() + ")");

        image.release();
        image = null;
    }
    return rgbLoadedImage;

}

I am calling this method after open CV has been loaded

 private BaseLoaderCallback  mLoaderCallback = new BaseLoaderCallback(this) {
    @Override
    public void onManagerConnected(int status) {
        switch (status) {
            case LoaderCallbackInterface.SUCCESS:
            {
                Log.i(TAG, "OpenCV loaded successfully...................");
                loadImageFromFile("pedestrian");

            } break;
            default:
            {
                super.onManagerConnected(status);
            } break;
        }
    }
};

I have also tried Mat m = Highgui.imread("/pedestrian"); here also m.width() is 0.