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Introduction

u can select a color in real time and it it track that color object and give u the position. i use aforge library for that also i used dotnetframework 4.0, it is a c# desktop application, it can take up to 25 frame per second .u can change color size any time u want, the color of drawing point will also be change

Background

I see a very interesting project in codeproject name making of lego pit camera, by help of this project i thought a realtime tracker could be made where color and objects size could also be changed in real time. and can draw movement of that objects in a bitmap with that color. i use some part of their code, although i use separate color filter for more accuracy.

Using the code

 The steps of work is very simple 

1.    take videoframe from webcam
2.    use filtering  by given color(here eucladianfiltering used)
3.    make greyscale
4.    find objects by given size
5.    find biggest object
6.    draw object position in  bitmap

First how my software work first can start tracking by default color black and color range of 120 but u can change in real time to color change press that a color dialog will come , then select color, remember to press OK and see the solidcolor box that Ur required color is present or not. 

To select the range and define minimum size of the object see next image, there are 3 numeric updown list for that. objectsize calculated in pixel now about the views,

 there are 4 view, 3 of them is Aforge video source control and another one is a picturebox, first one show normal video, second one show all detected object, 3rd box show only the biggest object and fourth one just draw a ’0′ sign in biggest object location, see below image for more clear view

i also add a richtextbox which showing the pixel of biggestrectangle position .now about the code for connection i use normal aforge connection code,

for that u need to download aforge dll, and  also add a very good videocontrol for showing video u can add it in ur toolbox. just click freespace on toolbox chooseitems-> browse the dll -> add the control

using AForge;
using AForge.Video.DirectShow;

then initialize

  videoDevices = new FilterInfoCollection(FilterCategory.VideoInputDevice);
               if (videoDevices.Count == 0)
                    throw new ApplicationException();
               foreach (FilterInfo device in videoDevices)
                {
VideoCaptureDevice videoSource = new VideoCaptureDevice(device.MonikerString);
 videoSource.DesiredFrameSize = new Size(320, 240);
 videoSource.DesiredFrameRate = 15;
videoSourcePlayer1.VideoSource = videoSource;
 videoSourcePlayer1.Start();
               }

for videoplayercontrol add a event in its misc
named

 private void videoSourcePlayer1_NewFrame(object sender, ref Bitmap image)
        {//work with image
}

in that function i apply my color detection code by writing eucladian filtering and then use blobcounter to extract data  , here i m explaining it

So see EuclideanColorFiltering work first see

we are going to apply a color filter it is very simple code to use euclideanfiltering

// create filter
EuclideanColorFiltering filter = new EuclideanColorFiltering( );
// set center colol and radius
filter.CenterColor = Color.FromArgb( 215, 30, 30 );
filter.Radius = 100;
// apply the filter
filter.ApplyInPlace( image );

now see the effect

well to understand how it work look closely at the code

filter.CenterColor = Color.FromArgb( 215, 30, 30 );
filter.Radius = 100;

first line select the select color value. you all know color has a value 0 to 255.
by filter.CenterColor = Color.FromArgb( 215, 30, 30 ); i specified my center color will be a red effected color because here value of red is 215, green and blue is 30. and filter.Radius = 100 means that all color value near than 100 in my specified color.
now my filter filters pixels, which color is inside/outside of RGB sphere with specified center and radius – it keeps pixels with colors inside/outside of the specified sphere and fills the rest with specified color.

Now for detect objects i use bitmap data and use lockbits method to understand clearly this method see here . then we make it greyscale algorithom hten unlock it. 

BitmapData objectsData = image.LockBits(new Rectangle(0, 0, image.Width, image.Height),ImageLockMode.ReadOnly, image.PixelFormat);
            // grayscaling
            UnmanagedImage grayImage = grayscaleFilter.Apply(new UnmanagedImage(objectsData));
            // unlock image
            image.UnlockBits(objectsData);

now the object we use blobcounter for that. it is a very strong class that aforge provided. 

  blobCounter.MinWidth = 5;
  blobCounter.MinHeight = 5;
  blobCounter.FilterBlobs = true;
  blobCounter.ProcessImage(grayImage);
  Rectangle[] rects = blobCounter.GetObjectRectangles();
  foreach(Rectangle recs in rects)
  if (rects.Length > 0)
   {
      foreach (Rectangle objectRect in rects)
   {

      Graphics g = Graphics.FromImage(image);

    using (Pen pen = new Pen(Color.FromArgb(160, 255, 160), 5))
                    {
                        g.DrawRectangle(pen, objectRect);
                    }

                    g.Dispose();
                }

            }

blobCounter.MinWidth and blobCounter.MinHeight define the smallest size of the object in pixel.
and blobCounter.GetObjectRectangles() return all the objects rectangle position. and using graphics class i draw rectangle over the images.

now if u want to take only the biggest object there is a method for that

   blobCounter.MinWidth = 5;
   blobCounter.MinHeight = 5;
   blobCounter.FilterBlobs = true;
   blobCounter.ObjectsOrder = ObjectsOrder.Size;
  blobCounter.ProcessImage(grayImage);
  Rectangle[] rects = blobCounter.GetObjectRectangles();
  foreach(Rectangle recs in rects)
    if (rects.Length > 0)
            {
                   Rectangle objectRect = rects[0];
                    Graphics g = Graphics.FromImage(image);
                    using (Pen pen = new Pen(Color.FromArgb(160, 255, 160), 5))
                    {
                        g.DrawRectangle(pen, objectRect);
                    }
                    g.Dispose();
                           }

now image is like that

but if u want to extract u can use following code

Bitmap bmp = new Bitmap(rects[0].Width, rects[0].Height);
Graphics g = Graphics.FromImage(bmp);
g.DrawImage(c, 0, 0, rects[0], GraphicsUnit.Pixel);

so u will get ur object like that

For draw the bitmap i had to use threading the thread was called in videosurecplayer event  where i called the thread. 

 void p(object r)
   {
       try
       {//create image
       Bitmap b = new Bitmap(pictureBox1.Image);
       Rectangle a = (Rectangle)r;
       Pen pen1 = new Pen(Color.FromArgb(160, 255, 160), 3);
       Graphics g2 = Graphics.FromImage(b);
       pen1 = new Pen(color, 3);
       SolidBrush b5 = new SolidBrush(color);
        Font f = new Font(Font, FontStyle.Bold);
       g2.DrawString("o", f, b5, a.Location);//draw the position
       g2.Dispose();
       pictureBox1.Image = (System.Drawing.Image)b;
       this.Invoke((MethodInvoker)delegate
           {
               richTextBox1.Text = a.Location.ToString() + "\n" + richTextBox1.Text + "\n"; ;
           });
       }
       catch (Exception faa)
       {
           Thread.CurrentThread.Abort();
       }
      Thread.CurrentThread.Abort();
   }

i have to use invoke to write in textbox because of cross threading.  To send rectangle object i use parameterized thread.  the thread 'aa' called the function "p()" to draw at bitmap and write in textbox.

 if (rects.Length > 0)
            {
                Rectangle objectRect = rects[0];

                // draw rectangle around derected object
                Graphics g = Graphics.FromImage(image);

                using (Pen pen = new Pen(Color.FromArgb(160, 255, 160), 5))
                {
                    g.DrawRectangle(pen, objectRect);
                }
              g.Dispose();
                int objectX = objectRect.X + objectRect.Width / 2 - image.Width / 2;
                int objectY = image.Height / 2 - (objectRect.Y + objectRect.Height / 2);
                ParameterizedThreadStart t = new ParameterizedThreadStart(p);
               Thread aa = new Thread(t);
               aa.Start(rects[0]);               
            } 

Points of Interest

 parameterized thrading, cross threading has to implement here, also there need to apply invoke method for write. u sing good threading we can increase the framerate. about filtering eucladian fltering is more accurate than HSLfiltering or Colorfiltering, yrbrcr filtering

 thanks to andrew kirillov  for his help.