How to detect face orientation changes on live preview ,face detection android

I am developing an app using google-face detection API, I have used the sample project, what I need is, I want to add the overlay image (mask) based on face orientation changes, eg: if face is rotated to right side or left side I want to update the overlayed image by taking the coordinate values.How to do this?.Can anyone help.Thanks in advance.

I have solved this issue by taking Euler Z value of detected face.I am posting my code:

I have rotated the rectangle and the mask bitmap on detected face when orientation changes;

RectF dest = new RectF((int) left, (int) top, (int) right, (int) bottom);

        Matrix m = new Matrix();

        m.setRotate(face.getEulerZ(),dest.centerX(),dest.centerY());
        m.mapRect(dest);

Rotated bitmap.

public Bitmap rotate_bitmap(Bitmap bmp,float degree){
    Matrix matrix = new Matrix();

    matrix.postRotate(degree);

    return Bitmap.createBitmap(bmp , 0, 0, bmp .getWidth(), bmp .getHeight(), matrix, true);
}

Drawing rotated mask on canvas.

            canvas.drawBitmap(rotate_bitmap(faceTrackerActivity.getBitmapItem("face"),face.getEulerZ()), null, dest, null);

Also, set FAST MODE to face detector.

FaceDetector detector = new FaceDetector.Builder(context)
            .setClassificationType(FaceDetector.ALL_CLASSIFICATIONS)


            .setMode(FaceDetector.FAST_MODE)
            .build();`