sustaining_gazes/gui/OpenFaceOffline/MainWindow.xaml.cs

///////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2017, Carnegie Mellon University and University of Cambridge,
// all rights reserved.
//
// ACADEMIC OR NON-PROFIT ORGANIZATION NONCOMMERCIAL RESEARCH USE ONLY
//
// BY USING OR DOWNLOADING THE SOFTWARE, YOU ARE AGREEING TO THE TERMS OF THIS LICENSE AGREEMENT.  
// IF YOU DO NOT AGREE WITH THESE TERMS, YOU MAY NOT USE OR DOWNLOAD THE SOFTWARE.
//
// License can be found in OpenFace-license.txt

//     * Any publications arising from the use of this software, including but
//       not limited to academic journal and conference publications, technical
//       reports and manuals, must cite at least one of the following works:
//
//       OpenFace: an open source facial behavior analysis toolkit
//       Tadas Baltrušaitis, Peter Robinson, and Louis-Philippe Morency
//       in IEEE Winter Conference on Applications of Computer Vision, 2016  
//
//       Rendering of Eyes for Eye-Shape Registration and Gaze Estimation
//       Erroll Wood, Tadas Baltrušaitis, Xucong Zhang, Yusuke Sugano, Peter Robinson, and Andreas Bulling 
//       in IEEE International. Conference on Computer Vision (ICCV),  2015 
//
//       Cross-dataset learning and person-speci?c normalisation for automatic Action Unit detection
//       Tadas Baltrušaitis, Marwa Mahmoud, and Peter Robinson 
//       in Facial Expression Recognition and Analysis Challenge, 
//       IEEE International Conference on Automatic Face and Gesture Recognition, 2015 
//
//       Constrained Local Neural Fields for robust facial landmark detection in the wild.
//       Tadas Baltrušaitis, Peter Robinson, and Louis-Philippe Morency. 
//       in IEEE Int. Conference on Computer Vision Workshops, 300 Faces in-the-Wild Challenge, 2013.    
//
///////////////////////////////////////////////////////////////////////////////

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
using System.Windows;
using System.Windows.Threading;
using System.Windows.Media.Imaging;

// Internal libraries
using OpenCVWrappers;
using CppInterop.LandmarkDetector;
using FaceAnalyser_Interop;
using GazeAnalyser_Interop;
using FaceDetectorInterop;
using UtilitiesOF;
using Microsoft.WindowsAPICodePack.Dialogs;
using System.Windows.Forms;

namespace OpenFaceOffline
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        // Timing for measuring FPS
        #region High-Resolution Timing
        static DateTime startTime;
        static Stopwatch sw = new Stopwatch();

        static MainWindow()
        {
            startTime = DateTime.Now;
            sw.Start();
        }

        public static DateTime CurrentTime
        {
            get { return startTime + sw.Elapsed; }
        }
        #endregion

        // -----------------------------------------------------------------
        // Members
        // -----------------------------------------------------------------

        Thread processing_thread;

        // Some members for displaying the results
        private WriteableBitmap latest_img;
        private WriteableBitmap latest_aligned_face;
        private WriteableBitmap latest_HOG_descriptor;

        // Managing the running of the analysis system
        private volatile bool thread_running;
        private volatile bool thread_paused = false;
        // Allows for going forward in time step by step
        // Useful for visualising things
        private volatile int skip_frames = 0;

        FpsTracker processing_fps = new FpsTracker();

        // For selecting webcams
        CameraSelection cam_sec;

        // For tracking
        FaceDetector face_detector;
        FaceModelParameters face_model_params;
        CLNF landmark_detector;

        // For face analysis
        FaceAnalyserManaged face_analyser;
        GazeAnalyserManaged gaze_analyser;

        public bool RecordAligned { get; set; } = false; // Aligned face images
        public bool RecordHOG { get; set; } = false; // HOG features extracted from face images
        public bool Record2DLandmarks { get; set; } = true; // 2D locations of facial landmarks (in pixels)
        public bool Record3DLandmarks { get; set; } = true; // 3D locations of facial landmarks (in pixels)
        public bool RecordModelParameters { get; set; } = true; // Facial shape parameters (rigid and non-rigid geometry)
        public bool RecordPose { get; set; } = true; // Head pose (position and orientation)
        public bool RecordAUs { get; set; } = true; // Facial action units
        public bool RecordGaze { get; set; } = true; // Eye gaze
        public bool RecordTracked { get; set; } = true; // Recording tracked videos or images

        // Visualisation options
        public bool ShowTrackedVideo { get; set; } = true; // Showing the actual tracking
        public bool ShowAppearance { get; set; } = true; // Showing appeaance features like HOG
        public bool ShowGeometry { get; set; } = true; // Showing geometry features, pose, gaze, and non-rigid
        public bool ShowAUs { get; set; } = true; // Showing Facial Action Units

        int image_output_size = 112;
        public bool MaskAligned { get; set; } = true; // Should the aligned images be masked

        // Where the recording is done (by default in a record directory, from where the application executed)
        String record_root = "./processed";

        // For AU prediction, if videos are long dynamic models should be used
        public bool DynamicAUModels { get; set; } = true;

        // Camera calibration parameters
        public float fx = -1, fy = -1, cx = -1, cy = -1;

        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = this; // For WPF data binding

            // Set the icon
            Uri iconUri = new Uri("logo1.ico", UriKind.RelativeOrAbsolute);
            this.Icon = BitmapFrame.Create(iconUri);
            
            String root = AppDomain.CurrentDomain.BaseDirectory;

            face_model_params = new FaceModelParameters(root, false);
            landmark_detector = new CLNF(face_model_params);

            gaze_analyser = new GazeAnalyserManaged();

        }

        // ----------------------------------------------------------
        // Actual work gets done here

        // Wrapper for processing multiple sequences
        private void ProcessSequences(List<String> filenames)
        {
            for (int i = 0; i < filenames.Count; ++i)
            {
                SequenceReader reader = new SequenceReader(filenames[i], false, fx, fy, cx, cy);
                ProcessSequence(reader);

                // Before continuing to next video make sure the user did not stop the processing
                if (!thread_running)
                {
                    break;
                }
            }

        }

        // The main function call for processing sequences
        private void ProcessSequence(SequenceReader reader)
        {
            Thread.CurrentThread.Priority = ThreadPriority.Highest;

            SetupFeatureExtractionMode();

            thread_running = true;

            face_model_params.optimiseForVideo();

            // Setup the visualization
            Visualizer visualizer_of = new Visualizer(ShowTrackedVideo || RecordTracked, ShowAppearance, ShowAppearance);

            // Initialize the face analyser
            face_analyser = new FaceAnalyserManaged(AppDomain.CurrentDomain.BaseDirectory, DynamicAUModels, image_output_size, MaskAligned);

            // Reset the tracker
            landmark_detector.Reset();

            // Loading an image file
            var frame = new RawImage(reader.GetNextImage());
            var gray_frame = new RawImage(reader.GetCurrentFrameGray());

            // Setup recording
            RecorderOpenFaceParameters rec_params = new RecorderOpenFaceParameters(true, reader.IsWebcam(),
                Record2DLandmarks, Record3DLandmarks, RecordModelParameters, RecordPose, RecordAUs,
                RecordGaze, RecordHOG, RecordTracked, RecordAligned,
                reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy(), reader.GetFPS());

            RecorderOpenFace recorder = new RecorderOpenFace(reader.GetName(), rec_params, record_root);

            // For FPS tracking
            DateTime? startTime = CurrentTime;
            var lastFrameTime = CurrentTime;

            // Empty image would indicate that the stream is over
            while (gray_frame.Width != 0)
            {
                if(!thread_running)
                {
                    break;
                }

                double progress = reader.GetProgress();
                bool detection_succeeding = landmark_detector.DetectLandmarksInVideo(gray_frame, face_model_params);

                // The face analysis step (for AUs and eye gaze)
                face_analyser.AddNextFrame(frame, landmark_detector.CalculateAllLandmarks(), detection_succeeding, false);
                gaze_analyser.AddNextFrame(landmark_detector, detection_succeeding, reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy());

                // Only the final face will contain the details
                VisualizeFeatures(frame, visualizer_of, landmark_detector.CalculateAllLandmarks(), landmark_detector.GetVisibilities(), detection_succeeding, true, reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy(), progress);

                // Record an observation
                RecordObservation(recorder, visualizer_of.GetVisImage(), detection_succeeding, reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy(), reader.GetTimestamp());

                while (thread_running & thread_paused && skip_frames == 0)
                {
                    Thread.Sleep(10);
                }

                if (skip_frames > 0)
                    skip_frames--;

                frame = new RawImage(reader.GetNextImage());
                gray_frame = new RawImage(reader.GetCurrentFrameGray());

                lastFrameTime = CurrentTime;
                processing_fps.AddFrame();
            }

            // Finalize the recording and flush to disk
            recorder.Close();

            // Post-process the AU recordings
            if(RecordAUs)
            { 
                face_analyser.PostProcessOutputFile(recorder.GetCSVFile());
            }

            // Close the open video/webcam
            reader.Close();

            EndMode();

        }

        private void ProcessIndividualImages(ImageReader reader)
        {
            // Make sure the GUI is setup appropriately
            SetupFeatureExtractionMode();

            // Indicate we will start running the thread
            thread_running = true;

            // Setup the parameters optimized for working on individual images rather than sequences
            face_model_params.optimiseForImages();

            // Setup the visualization
            Visualizer visualizer_of = new Visualizer(ShowTrackedVideo || RecordTracked, ShowAppearance, ShowAppearance);

            // Initialize the face detector if it has not been initialized yet
            if (face_detector == null)
            {
                face_detector = new FaceDetector();
            }

            // Initialize the face analyser
            face_analyser = new FaceAnalyserManaged(AppDomain.CurrentDomain.BaseDirectory, false, image_output_size, MaskAligned);

            // Loading an image file
            var frame = new RawImage(reader.GetNextImage());
            var gray_frame = new RawImage(reader.GetCurrentFrameGray());

            // For FPS tracking
            DateTime? startTime = CurrentTime;
            var lastFrameTime = CurrentTime;

            // This will be false when the image is not available
            while (reader.isOpened())
            {
                if (!thread_running)
                {
                    break;
                }

                // Setup recording
                RecorderOpenFaceParameters rec_params = new RecorderOpenFaceParameters(false, false,
                    Record2DLandmarks, Record3DLandmarks, RecordModelParameters, RecordPose, RecordAUs,
                    RecordGaze, RecordHOG, RecordTracked, RecordAligned,
                    reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy(), 0);

                RecorderOpenFace recorder = new RecorderOpenFace(reader.GetName(), rec_params, record_root);

                // Detect faces here and return bounding boxes
                List<Rect> face_detections = new List<Rect>();
                List<double> confidences = new List<double>();
                face_detector.DetectFacesHOG(face_detections, gray_frame, confidences);

                // For visualization
                double progress = reader.GetProgress();

                for (int i = 0; i < face_detections.Count; ++i)
                {
                    bool detection_succeeding = landmark_detector.DetectFaceLandmarksInImage(gray_frame, face_detections[i], face_model_params);

                    var landmarks = landmark_detector.CalculateAllLandmarks();
                    
                    // Predict action units
                    var au_preds = face_analyser.PredictStaticAUsAndComputeFeatures(frame, landmarks);

                    // Predic eye gaze
                    gaze_analyser.AddNextFrame(landmark_detector, detection_succeeding, reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy());

                    // Only the final face will contain the details
                    VisualizeFeatures(frame, visualizer_of, landmarks, landmark_detector.GetVisibilities(), detection_succeeding, i == 0, reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy(), progress);

                    // Record an observation
                    RecordObservation(recorder, visualizer_of.GetVisImage(), detection_succeeding, reader.GetFx(), reader.GetFy(), reader.GetCx(), reader.GetCy(), 0);

                }

                frame = new RawImage(reader.GetNextImage());
                gray_frame = new RawImage(reader.GetCurrentFrameGray());

                // Do not cary state accross images
                landmark_detector.Reset();
                face_analyser.Reset();
                recorder.Close();

                lastFrameTime = CurrentTime;
                processing_fps.AddFrame();
                
                // TODO how to report errors from the reader here? exceptions? logging? Problem for future versions?
            }

            EndMode();

        }

        private void RecordObservation(RecorderOpenFace recorder, RawImage vis_image, bool success, float fx, float fy, float cx, float cy, double timestamp)
        {

            recorder.SetObservationTimestamp(timestamp);

            double confidence = landmark_detector.GetConfidence();

            List<double> pose = new List<double>();
            landmark_detector.GetPose(pose, fx, fy, cx, cy);
            recorder.SetObservationPose(pose);

            List<Tuple<double, double>> landmarks_2D = landmark_detector.CalculateAllLandmarks();
            List<Tuple<double, double, double>> landmarks_3D = landmark_detector.Calculate3DLandmarks(fx, fy, cx, cy);
            List<double> global_params = landmark_detector.GetRigidParams();
            List<double> local_params = landmark_detector.GetNonRigidParams();

            recorder.SetObservationLandmarks(landmarks_2D, landmarks_3D, global_params, local_params, confidence, success);

            var gaze = gaze_analyser.GetGazeCamera();
            var gaze_angle = gaze_analyser.GetGazeAngle();

            var landmarks_2d_eyes = landmark_detector.CalculateAllEyeLandmarks();
            var landmarks_3d_eyes = landmark_detector.CalculateAllEyeLandmarks3D(fx, fy, cx, cy);
            recorder.SetObservationGaze(gaze.Item1, gaze.Item2, gaze_angle, landmarks_2d_eyes, landmarks_3d_eyes);

            var au_regs = face_analyser.GetCurrentAUsReg();
            var au_classes = face_analyser.GetCurrentAUsClass();
            recorder.SetObservationActionUnits(au_regs, au_classes);

            recorder.SetObservationFaceAlign(face_analyser.GetLatestAlignedFace());
            
            var hog_feature = face_analyser.GetLatestHOGFeature();
            recorder.SetObservationHOG(success, hog_feature, face_analyser.GetHOGRows(), face_analyser.GetHOGCols(), face_analyser.GetHOGChannels());

            recorder.SetObservationVisualization(vis_image);

            recorder.WriteObservation();


        }

        private void VisualizeFeatures(RawImage frame, Visualizer visualizer, List<Tuple<double, double>> landmarks, List<bool> visibilities, bool detection_succeeding, 
            bool new_image, float fx, float fy, float cx, float cy, double progress)
        {

            List<Tuple<Point, Point>> lines = null;
            List<Tuple<double, double>> eye_landmarks = null;
            List<Tuple<Point, Point>> gaze_lines = null;
            Tuple<double, double> gaze_angle = new Tuple<double, double>(0, 0);

            List<double> pose = new List<double>();
            landmark_detector.GetPose(pose, fx, fy, cx, cy);
            List<double> non_rigid_params = landmark_detector.GetNonRigidParams();

            double confidence = landmark_detector.GetConfidence();

            if (confidence < 0)
                confidence = 0;
            else if (confidence > 1)
                confidence = 1;

            double scale = landmark_detector.GetRigidParams()[0];

            // Helps with recording and showing the visualizations
            if (new_image)
            {
                visualizer.SetImage(frame, fx, fy, cx, cy);
            }
            visualizer.SetObservationHOG(face_analyser.GetLatestHOGFeature(), face_analyser.GetHOGRows(), face_analyser.GetHOGCols());
            visualizer.SetObservationLandmarks(landmarks, confidence, visibilities);
            visualizer.SetObservationPose(pose, confidence);
            visualizer.SetObservationGaze(gaze_analyser.GetGazeCamera().Item1, gaze_analyser.GetGazeCamera().Item2, landmark_detector.CalculateAllEyeLandmarks(), landmark_detector.CalculateAllEyeLandmarks3D(fx, fy, cx, cy), confidence);

            if (detection_succeeding)
            {                
                eye_landmarks = landmark_detector.CalculateVisibleEyeLandmarks();
                lines = landmark_detector.CalculateBox(fx, fy, cx, cy);

                gaze_lines = gaze_analyser.CalculateGazeLines(fx, fy, cx, cy);
                gaze_angle = gaze_analyser.GetGazeAngle();
            }

            // Visualisation (as a separate function)
            Dispatcher.Invoke(DispatcherPriority.Render, new TimeSpan(0, 0, 0, 0, 200), (Action)(() =>
            {
                if (ShowAUs)
                {
                    var au_classes = face_analyser.GetCurrentAUsClass();
                    var au_regs = face_analyser.GetCurrentAUsReg();

                    auClassGraph.Update(au_classes);

                    var au_regs_scaled = new Dictionary<String, double>();
                    foreach (var au_reg in au_regs)
                    {
                        au_regs_scaled[au_reg.Key] = au_reg.Value / 5.0;
                        if (au_regs_scaled[au_reg.Key] < 0)
                            au_regs_scaled[au_reg.Key] = 0;

                        if (au_regs_scaled[au_reg.Key] > 1)
                            au_regs_scaled[au_reg.Key] = 1;
                    }
                    auRegGraph.Update(au_regs_scaled);
                }

                if (ShowGeometry)
                {
                    int yaw = (int)(pose[4] * 180 / Math.PI + 0.5);
                    int roll = (int)(pose[5] * 180 / Math.PI + 0.5);
                    int pitch = (int)(pose[3] * 180 / Math.PI + 0.5);

                    YawLabel.Content = yaw + "°";
                    RollLabel.Content = roll + "°";
                    PitchLabel.Content = pitch + "°";

                    XPoseLabel.Content = (int)pose[0] + " mm";
                    YPoseLabel.Content = (int)pose[1] + " mm";
                    ZPoseLabel.Content = (int)pose[2] + " mm";

                    nonRigidGraph.Update(non_rigid_params);

                    // Update eye gaze
                    String x_angle = String.Format("{0:F0}°", gaze_angle.Item1 * (180.0 / Math.PI));
                    String y_angle = String.Format("{0:F0}°", gaze_angle.Item2 * (180.0 / Math.PI));
                    GazeXLabel.Content = x_angle;
                    GazeYLabel.Content = y_angle;
                }

                if (ShowTrackedVideo)
                {
                    if (new_image)
                    {
                        latest_img = frame.CreateWriteableBitmap();
                    }
                    
                    frame.UpdateWriteableBitmap(latest_img);

                    overlay_image.Source = latest_img;
                    overlay_image.Confidence = confidence;
                    overlay_image.FPS = processing_fps.GetFPS();
                    overlay_image.Progress = progress;
                    overlay_image.FaceScale = scale;

                    if (!detection_succeeding)
                    {
                        overlay_image.OverlayLines.Clear();
                        overlay_image.OverlayPoints.Clear();
                        overlay_image.OverlayPointsVisibility.Clear();
                        overlay_image.OverlayEyePoints.Clear();
                        overlay_image.GazeLines.Clear();
                    }
                    else
                    {

                        List<Point> landmark_points = new List<Point>();
                        foreach (var p in landmarks)
                        {
                            landmark_points.Add(new Point(p.Item1, p.Item2));
                        }

                        List<Point> eye_landmark_points = new List<Point>();
                        foreach (var p in eye_landmarks)
                        {
                            eye_landmark_points.Add(new Point(p.Item1, p.Item2));
                        }


                        if (new_image)
                        {
                            overlay_image.OverlayLines = lines;
                            overlay_image.OverlayPoints = landmark_points;
                            overlay_image.OverlayPointsVisibility = visibilities;
                            overlay_image.OverlayEyePoints = eye_landmark_points;
                            overlay_image.GazeLines = gaze_lines;
                        }
                        else
                        {
                            // In case of multiple faces just add them to the existing drawing list
                            overlay_image.OverlayLines.AddRange(lines.GetRange(0, lines.Count));
                            overlay_image.OverlayPoints.AddRange(landmark_points.GetRange(0, landmark_points.Count));
                            overlay_image.OverlayPointsVisibility.AddRange(visibilities.GetRange(0, visibilities.Count));
                            overlay_image.OverlayEyePoints.AddRange(eye_landmark_points.GetRange(0, eye_landmark_points.Count));
                            overlay_image.GazeLines.AddRange(gaze_lines.GetRange(0, gaze_lines.Count));
                        }
                    }
                }

                if (ShowAppearance)
                {
                    RawImage aligned_face = face_analyser.GetLatestAlignedFace();
                    RawImage hog_face = visualizer.GetHOGVis();

                    if (latest_aligned_face == null)
                    {
                        latest_aligned_face = aligned_face.CreateWriteableBitmap();
                        latest_HOG_descriptor = hog_face.CreateWriteableBitmap();
                    }

                    aligned_face.UpdateWriteableBitmap(latest_aligned_face);
                    hog_face.UpdateWriteableBitmap(latest_HOG_descriptor);

                    AlignedFace.Source = latest_aligned_face;
                    AlignedHOG.Source = latest_HOG_descriptor;
                }
            }));


        }

        private void StopTracking()
        {
            // First complete the running of the thread
            if (processing_thread != null)
            {
                // Tell the other thread to finish
                thread_running = false;
                processing_thread.Join();
            }
        }


        // ----------------------------------------------------------
        // Mode handling (image, video)
        // ----------------------------------------------------------

        // Disable GUI components that should not be active during processing
        private void SetupFeatureExtractionMode()
        {
            Dispatcher.Invoke((Action)(() =>
            {
                SettingsMenu.IsEnabled = false;
                RecordingMenu.IsEnabled = false;
                AUSetting.IsEnabled = false;

                PauseButton.IsEnabled = true;
                StopButton.IsEnabled = true;
                NextFiveFramesButton.IsEnabled = false;
                NextFrameButton.IsEnabled = false;
            }));
        }

        // When the processing is done re-enable the components
        private void EndMode()
        {
            latest_img = null;
            skip_frames = 0;

            // Unpause if it's paused
            if (thread_paused)
            {
                Dispatcher.Invoke(DispatcherPriority.Render, new TimeSpan(0, 0, 0, 0, 200), (Action)(() =>
                {
                    PauseButton_Click(null, null);
                }));
            }

            Dispatcher.Invoke(DispatcherPriority.Render, new TimeSpan(0, 0, 0, 1, 0), (Action)(() =>
            {

                SettingsMenu.IsEnabled = true;
                RecordingMenu.IsEnabled = true;
                AUSetting.IsEnabled = true;

                PauseButton.IsEnabled = false;
                StopButton.IsEnabled = false;
                NextFiveFramesButton.IsEnabled = false;
                NextFrameButton.IsEnabled = false;

                // Clean up the interface itself
                overlay_image.Source = null;
                
                auClassGraph.Update(new Dictionary<string, double>());
                auRegGraph.Update(new Dictionary<string, double>());
                YawLabel.Content = "0°";
                RollLabel.Content = "0°";
                PitchLabel.Content = "0°";

                XPoseLabel.Content = "0 mm";
                YPoseLabel.Content = "0 mm";
                ZPoseLabel.Content = "0 mm";

                nonRigidGraph.Update(new List<double>());

                GazeXLabel.Content = "0°";
                GazeYLabel.Content = "0°";
                
                AlignedFace.Source = null;
                AlignedHOG.Source = null;

            }));
        }

        // ----------------------------------------------------------
        // Opening Videos/Images
        // ----------------------------------------------------------

        // Some utilities for opening images/videos and directories
        private List<string> openMediaDialog(bool images)
        {
            string[] image_files = new string[0];
            Dispatcher.Invoke(DispatcherPriority.Render, new TimeSpan(0, 0, 0, 2, 0), (Action)(() =>
            {
                var d = new Microsoft.Win32.OpenFileDialog();
                d.Multiselect = true;
                if (images)
                {
                    d.Filter = "Image files|*.jpg;*.jpeg;*.bmp;*.png;*.gif";
                }
                else
                {
                    d.Filter = "Video files|*.avi;*.wmv;*.mov;*.mpg;*.mpeg;*.mp4";
                }
                if (d.ShowDialog(this) == true)
                {

                    image_files = d.FileNames;

                }
            }));
            List<string> img_files_list = new List<string>(image_files);
            return img_files_list;
        }

        private string openDirectory()
        {
            string to_return = "";
            using (var fbd = new FolderBrowserDialog())
            {
                DialogResult result = fbd.ShowDialog();
                if (result == System.Windows.Forms.DialogResult.OK)
                {
                    to_return = fbd.SelectedPath;
                }
                else if(!string.IsNullOrWhiteSpace(fbd.SelectedPath))
                {
                    string messageBoxText = "Could not open the directory.";
                    string caption = "Invalid directory";
                    MessageBoxButton button = MessageBoxButton.OK;
                    MessageBoxImage icon = MessageBoxImage.Warning;

                    // Display message box
                    System.Windows.MessageBox.Show(messageBoxText, caption, button, icon);

                }
            }
            return to_return;
        }

        private void imageSequenceFileOpenClick(object sender, RoutedEventArgs e)
        {
            // First clean up existing tracking
            StopTracking();

            string directory = openDirectory();
            if (!string.IsNullOrWhiteSpace(directory))
            {
                SequenceReader reader = new SequenceReader(directory, true, fx, fy, cx, cy);

                processing_thread = new Thread(() => ProcessSequence(reader));
                processing_thread.Name = "Image sequence processing";
                processing_thread.Start();
            }

        }

        private void videoFileOpenClick(object sender, RoutedEventArgs e)
        {
            // First clean up existing tracking
            StopTracking();

            var video_files = openMediaDialog(false);
            processing_thread = new Thread(() => ProcessSequences(video_files));
            processing_thread.Name = "Video processing";
            processing_thread.Start();

        }

        // Selecting one or more images in a directory
        private void individualImageFilesOpenClick(object sender, RoutedEventArgs e)
        {
            // First clean up existing tracking
            StopTracking();

            var image_files = openMediaDialog(true);
            ImageReader reader = new ImageReader(image_files, fx, fy, cx, cy);

            processing_thread = new Thread(() => ProcessIndividualImages(reader));
            processing_thread.Start();

        }

        // Selecting a directory containing images
        private void individualImageDirectoryOpenClick(object sender, RoutedEventArgs e)
        {
            
            // First clean up existing tracking
            StopTracking();

            string directory = openDirectory();
            if(!string.IsNullOrWhiteSpace(directory))
            { 
                ImageReader reader = new ImageReader(directory, fx, fy, cx, cy);

                processing_thread = new Thread(() => ProcessIndividualImages(reader));
                processing_thread.Start();
            }
        }

        private void openWebcamClick(object sender, RoutedEventArgs e)
        {
            StopTracking();

            // If camera selection has already been done, no need to re-populate the list as it is quite slow
            if (cam_sec == null)
            {
                cam_sec = new CameraSelection();
            }
            else
            {
                cam_sec = new CameraSelection(cam_sec.cams);
                cam_sec.Visibility = System.Windows.Visibility.Visible;
            }

            // Set the icon
            Uri iconUri = new Uri("logo1.ico", UriKind.RelativeOrAbsolute);
            cam_sec.Icon = BitmapFrame.Create(iconUri);

            if (!cam_sec.no_cameras_found)
                cam_sec.ShowDialog();

            if (cam_sec.camera_selected)
            {
                int cam_id = cam_sec.selected_camera.Item1;
                int width = cam_sec.selected_camera.Item2;
                int height = cam_sec.selected_camera.Item3;

                SequenceReader reader = new SequenceReader(cam_id, width, height, fx, fy, cx, cy);

                processing_thread = new Thread(() => ProcessSequence(reader));
                processing_thread.Name = "Webcam processing";
                processing_thread.Start();

            }
        }


        // --------------------------------------------------------
        // Button handling
        // --------------------------------------------------------

        // Cleanup stuff when closing the window
        private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            if (processing_thread != null)
            {
                // Stop capture and tracking
                thread_running = false;
                processing_thread.Join();
            }
        }

        // Stopping the tracking
        private void StopButton_Click(object sender, RoutedEventArgs e)
        {
            if (processing_thread != null)
            {
                // Stop capture and tracking
                thread_paused = false;
                thread_running = false;
                // Let the processing thread finish
                processing_thread.Join();

                // Clean up the interface
                EndMode();
            }
        }

        private void PauseButton_Click(object sender, RoutedEventArgs e)
        {
            if (processing_thread != null)
            {
                // Stop capture and tracking                
                thread_paused = !thread_paused;

                NextFrameButton.IsEnabled = thread_paused;
                NextFiveFramesButton.IsEnabled = thread_paused;

                if (thread_paused)
                {
                    PauseButton.Content = "Resume";
                }
                else
                {
                    PauseButton.Content = "Pause";
                }
            }
        }

        private void SkipButton_Click(object sender, RoutedEventArgs e)
        {
            if (sender.Equals(NextFrameButton))
            {
                skip_frames += 1;
            }
            else if (sender.Equals(NextFiveFramesButton))
            {
                skip_frames += 5;
            }
        }


        private void VisualisationChange(object sender, RoutedEventArgs e)
        {
            // Collapsing or restoring the windows here
            if (!ShowTrackedVideo)
            {
                VideoBorder.Visibility = System.Windows.Visibility.Collapsed;
                MainGrid.ColumnDefinitions[0].Width = new GridLength(0, GridUnitType.Star);
            }
            else
            {
                VideoBorder.Visibility = System.Windows.Visibility.Visible;
                MainGrid.ColumnDefinitions[0].Width = new GridLength(2.1, GridUnitType.Star);
            }

            if (!ShowAppearance)
            {
                AppearanceBorder.Visibility = System.Windows.Visibility.Collapsed;
                MainGrid.ColumnDefinitions[1].Width = new GridLength(0, GridUnitType.Star);
            }
            else
            {
                AppearanceBorder.Visibility = System.Windows.Visibility.Visible;
                MainGrid.ColumnDefinitions[1].Width = new GridLength(0.8, GridUnitType.Star);
            }

            // Collapsing or restoring the windows here
            if (!ShowGeometry)
            {
                GeometryBorder.Visibility = System.Windows.Visibility.Collapsed;
                MainGrid.ColumnDefinitions[2].Width = new GridLength(0, GridUnitType.Star);
            }
            else
            {
                GeometryBorder.Visibility = System.Windows.Visibility.Visible;
                MainGrid.ColumnDefinitions[2].Width = new GridLength(1.0, GridUnitType.Star);
            }

            // Collapsing or restoring the windows here
            if (!ShowAUs)
            {
                ActionUnitBorder.Visibility = System.Windows.Visibility.Collapsed;
                MainGrid.ColumnDefinitions[3].Width = new GridLength(0, GridUnitType.Star);
            }
            else
            {
                ActionUnitBorder.Visibility = System.Windows.Visibility.Visible;
                MainGrid.ColumnDefinitions[3].Width = new GridLength(1.6, GridUnitType.Star);
            }

        }
       
        private void setOutputImageSize_Click(object sender, RoutedEventArgs e)
        {

            NumberEntryWindow number_entry_window = new NumberEntryWindow(image_output_size);
            number_entry_window.Icon = this.Icon;

            number_entry_window.WindowStartupLocation = WindowStartupLocation.CenterScreen;

            if (number_entry_window.ShowDialog() == true)
            {
                image_output_size = number_entry_window.OutputInt;
            }
        }

        private void setCameraParameters_Click(object sender, RoutedEventArgs e)
        {
            CameraParametersEntry camera_params_entry_window = new CameraParametersEntry(fx, fy, cx, cy);
            camera_params_entry_window.Icon = this.Icon;

            camera_params_entry_window.WindowStartupLocation = WindowStartupLocation.CenterScreen;

            if (camera_params_entry_window.ShowDialog() == true)
            {
                fx = camera_params_entry_window.Fx;
                fy = camera_params_entry_window.Fy;
                cx = camera_params_entry_window.Cx;
                cy = camera_params_entry_window.Cy;
            }
        }

        private void OutputLocationItem_Click(object sender, RoutedEventArgs e)
        {
            var dlg = new CommonOpenFileDialog();
            dlg.Title = "Select output directory";
            dlg.IsFolderPicker = true;
            dlg.AllowNonFileSystemItems = false;
            dlg.EnsureFileExists = true;
            dlg.EnsurePathExists = true;
            dlg.EnsureReadOnly = false;
            dlg.EnsureValidNames = true;
            dlg.Multiselect = false;
            dlg.ShowPlacesList = true;

            if (dlg.ShowDialog() == CommonFileDialogResult.Ok)
            {
                var folder = dlg.FileName;
                record_root = folder;
            }
        }

    }
}