Gesture Recognition for Touch Devices (Touch Gestures)

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Threading;

namespace TouchGestures
{
    public class GestureTracker
    {
        // a list of all the points which the mouse traversed
        List<Point> points = new List<Point>();
        // a reference for the canvas in MainWindow.xaml
        readonly Canvas canvas;
        // a timer for removing the rectangle boundary from the gesture image
        DispatcherTimer timer = new DispatcherTimer();
        // name of the recognised gesture
        string gesture = string.Empty;
        // randomly generated name for a rectangle
        string rectangleName = string.Empty;

        // prefix img to the gesture name so that we can select which image to highlight
        private string GetImageNameFromGesture
        {
            get
            {
                return (!string.IsNullOrEmpty(gesture))? string.Format("img{0}", gesture) : string.Empty;
            }
        }

        // generate a new guid and replace minus signs from it
        private string GenerateNewGuidLessMinus()
        {
            return Guid.NewGuid().ToString().Replace("-", string.Empty);
        }

        public GestureTracker(Canvas canvasParam)
        {
            canvas = canvasParam;

            // set timer for the highlighting rectangle to 2 seconds
            timer.Interval = TimeSpan.FromSeconds(2);
            timer.Tick += new EventHandler(highlightTimer_Tick);
        }

        public void ProcessDown(Point location)
        {
            // add point to the gesture's points list
            points.Add(location);
        }

        public void ProcessMove(Point location)
        {
            // add point to the gesture's points list
            points.Add(location);
        }

        public void ProcessUp(Point location)
        {
            // add point to the gesture's points list
            points.Add(location);

            // process and recognize the gesture
            gesture = GestureInterpreter.InterpretGesture(points);

            // find coordinates of the image for the recognized gesture
            Point imageCoordinates = FindImageCoordinatesByGesture();
            // add a boundary to the rectangle, so that it gives a highlight effect
            // pass the left and top coordinates of the image
            AddHighlightToImage(imageCoordinates.X, imageCoordinates.Y);
            
            // start a delay for 2 seconds and in the tick event
            // we remove the rectangle (border) from the image
            // which gives a un-highlighting effect
            timer.Start();
        }

        private Point FindImageCoordinatesByGesture()
        {
            // get the image object by using its name
            Image image = canvas.FindName(GetImageNameFromGesture) as Image;
            Point point = new Point(Canvas.GetLeft(image), Canvas.GetTop(image));
            // return the left and top of the image in a point object
            return point;
        }

        // highlight the image by adding a rectangle boundary around it
        private void AddHighlightToImage(double left, double top)
        {
            Rectangle rectangle = new Rectangle();
            // create a random name for this rectangle
            // this is just to ensure that we don't fail while adding/registering the 
            // rectangle as a children of canvas
            rectangleName = string.Format("rect{0}", GenerateNewGuidLessMinus());
            rectangle.Name = rectangleName;

            // set some generic properties
            rectangle.Width = 72;
            rectangle.Height = 72;
            rectangle.StrokeThickness = 2;
            rectangle.RadiusX = 3;
            rectangle.RadiusY = 3;

            // create a random color for this rectangle
            Random random = new Random((int)DateTime.Now.Millisecond);
            SolidColorBrush brush = new SolidColorBrush(Color.FromRgb((byte)random.Next(0, 255), (byte)random.Next(0, 255), (byte)random.Next(0, 255)));
            rectangle.Stroke = brush;

            // set the coordinates of the rectangle
            Canvas.SetLeft(rectangle, left);
            Canvas.SetTop(rectangle, top);
            // register the name of rectangle with canvas
            // and add it to childres list of canvas
            canvas.RegisterName(rectangleName, rectangle);
            canvas.Children.Insert(0, rectangle);
        }

        private void highlightTimer_Tick(object sender, EventArgs e)
        {
            // remove the boundary from the image
            // or actually remove the rectangle that we added earlier from canvas 
            RemoveHighlightFromImage();
            // disable and stop the timer
            timer.Stop();
        }

        // remove the highlight boundary from the image
        // in actual remove the rectangle that we added a few seconds ago
        private void RemoveHighlightFromImage()
        {
            // find the rectangle by the registered name
            Rectangle rectangle = (Rectangle)canvas.FindName(rectangleName);
            // change the color of boundary
            rectangle.Stroke = new SolidColorBrush(Colors.White);
            // remove from childres list and unregister the name
            canvas.Children.Remove(rectangle);
            canvas.UnregisterName(rectangleName);
        }
    }
}