How to measure FPS of an OpenCV camera preview?

Android/Java
6

That’s a great suggestion, seeing as though I’m unable to edit my original post to implement the necessary relevant code, I will paste it here in this comment. In developing this application, I had used this OpenCV tutorial in guiding myself.

MainActivity.java

public class MainActivity extends AppCompatActivity implements CameraBridgeViewBase.CvCameraViewListener2 {

 //initialize OpenCV manager.
 private BaseLoaderCallback baseLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            switch (status) {
                case LoaderCallbackInterface.SUCCESS: {
                    Log.i(TAG, "OpenCV loaded successfully");
                    mOpenCvCameraView.enableView();
                    break;
                }
                default: {
                    super. onManagerConnected(status);
                    break;
                }
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //Set up a camera listener.
        mOpenCvCameraView = (CameraBridgeViewBase)findViewById(R.id.CameraView);
        mOpenCvCameraView.setVisibility(CameraBridgeViewBase.VISIBLE);
        mOpenCvCameraView.setCvCameraViewListener(this);

        //Checking if the permission has already been granted
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                == PackageManager.PERMISSION_GRANTED) {
            Log.d(TAG, "Permissions granted");
            initializeCamera((JavaCameraView) mOpenCvCameraView, activeCamera);
        } else {
            //prompt system dialogue
            Log.d(TAG, "Permission prompt");
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, MY_CAMERA_REQUEST_CODE);
        }
    }

    //Load a network.
    @Override
    public void onCameraViewStarted(int width, int height) {
        String proto = getPath("MobileNetSSD_deploy.prototxt", this);
        String weights = getPath("MobileNetSSD_deploy.caffemodel", this);
        net = Dnn.readNetFromCaffe(proto, weights);
        Log.i(TAG, "Network loaded successfully");

    }

    @Override
    public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
        //return null;
        final int IN_WIDTH = 300;
        final int IN_HEIGHT = 300;
        final float WH_RATIO = (float)IN_WIDTH / IN_HEIGHT;
        final double IN_SCALE_FACTOR = 0.007843;
        final double MEAN_VAL = 127.5;
        final double THRESHOLD = 0.2;

        //Get a new frame
        Mat frame = inputFrame.rgba();
        Imgproc.cvtColor(frame, frame, Imgproc.COLOR_RGBA2RGB);

        //Forward image through network.
        Mat blob = Dnn.blobFromImage(frame, IN_SCALE_FACTOR,
                new Size(IN_WIDTH, IN_HEIGHT),
                new Scalar(MEAN_VAL, MEAN_VAL, MEAN_VAL), false, false);
        net.setInput(blob);
        Mat detections = net.forward();

        int cols = frame.cols();
        int rows = frame.rows();

        detections = detections.reshape(1, (int)detections.total() / 7);

        for (int i = 0; i < detections.rows(); ++i) {
            double confidence = detections.get(i,2)[0];
            if (confidence > THRESHOLD) {
                int classId = (int)detections.get(i,1)[0];

                int left   = (int)(detections.get(i,3)[0] * cols);
                int top    = (int)(detections.get(i,4)[0] * rows);
                int right  = (int)(detections.get(i,5)[0] * cols);
                int bottom = (int)(detections.get(i,6)[0] * rows);

                //Draw rectangle around detected object.
                Imgproc.rectangle(frame, new Point(left,top), new Point(right,bottom),
                        new Scalar(0, 255, 0));
                String label = classNames[classId] + ": " + confidence;
                int[] baseLine = new int[1];
                Size labelSize = Imgproc.getTextSize(label, Imgproc.FONT_HERSHEY_SIMPLEX, 0.5, 1, baseLine);

                //Draw background for label.
                Imgproc.rectangle(frame, new Point(left, top - labelSize.height),
                        new Point(left + labelSize.width, top + baseLine[0]),
                        new Scalar(255, 255, 255), Imgproc.FILLED);
                //Write class name and confidence.
                Imgproc.putText(frame, label, new Point(left, top),
                        Imgproc.FONT_HERSHEY_SIMPLEX, 0.5, new Scalar(0, 0, 0));
            }
        }
        return frame;
    }

    private void initializeCamera(JavaCameraView mOpenCvCameraView, int activeCamera){
        mOpenCvCameraView.setCameraPermissionGranted();
        mOpenCvCameraView.setCameraIndex(activeCamera);
        mOpenCvCameraView.setVisibility(CameraBridgeViewBase.VISIBLE);
        mOpenCvCameraView.setCvCameraViewListener(this);
    }