Introduction

Using C# code and Aforge library, we can easily detect and extract the pupil from an eye image.

Algorithm

  • Step 1 - First take the eye image.
  • Step 2 - Make it invert.
  • Step 3 - Convert it to gray scale.
  • Step 4 - Use binary filter taking threshold value 220.
  • Step 5 - Find the biggest object.
  • Step 6 - Find that objects center point and height.
  • Step 7 - Cut a circle from that point taking radius as 2.5 multiply of height.

eyeaaaaaaaaaaaa1.jpg - Click to enlarge image

Using the Code

The code is quite easy, using the aforge library filters invert, grayscale and threshold filters. First see the full code and then I will describe it. 

System.Drawing.Bitmap aq = (Bitmap)pictureBox1.Image; //take the image
                     //////inverting the image
Invert a = new Invert();
aq=    a.Apply(aq);
AForge.Imaging.Image.FormatImage(ref aq);
 
                      /// apply grayscale
IFilter  filter =  Grayscale.CommonAlgorithms.BT709;
aq = filter.Apply(aq);
  
Threshold th = new Threshold(220);
aq = th.Apply(aq);
 
                            ///find the biggest object
BlobCounter bl = new BlobCounter(aq);
int i = bl.ObjectsCount;
ExtractBiggestBlob fil2 = new ExtractBiggestBlob();
 /// find the eye pupils start position and height
 
 int x = 0;
 int y = 0;
 int h = 0;
   if (i > 0)
   {
       fil2.Apply(aq);
       x  = fil2.BlobPosition.X;
       y = fil2.BlobPosition.Y;
      
        h = fil2.Apply(aq).Height;
   }
  
   System.Drawing.Bitmap Bitmapsource = (Bitmap)pictureBox1.Image;
   Rectangle section = new Rectangle(new Point(x -  h, y - h), new Size(3 * h, 3 *h));
   
   Bitmap CroppedImage = CropImage(Bitmapsource, section);
   pictureBox6.Image = CroppedImage;//get the eye pupil image

First, take the eye image:

System.Drawing.Bitmap aq = (Bitmap)pictureBox1.Image;

Then make it invert:

Invert a = new Invert();
aq=    a.Apply(aq);
AForge.Imaging.Image.FormatImage(ref aq);

Now we make it grayscale:

 IFilter  filter =  Grayscale.CommonAlgorithms.BT709;
                         aq = filter.Apply(aq);

Now we make it binary using threshold 220:

Threshold th = new Threshold(220);
          aq = th.Apply(aq);

Now we have to find the biggest object in the binary image:

BlobCounter bl = new BlobCounter(aq);
         int i = bl.ObjectsCount;
ExtractBiggestBlob fil2 = new ExtractBiggestBlob();
         fil2.Apply(aq);

Now we will find the start position and height of the biggest object/eye pupil:

int x = 0;
         int y = 0;
         int h = 0;
           if (i > 0)
           {
               fil2.Apply(aq);
               x  = fil2.BlobPosition.X;
               y = fil2.BlobPosition.Y;

                h = fil2.Apply(aq).Height;
           }

Now, we have to cut the pupil part from the image so we can find the image:

To cut the image, we use the following code:

System.Drawing.Bitmap Bitmapsource = (Bitmap)pictureBox1.Image;
Rectangle section = new Rectangle(new Point(x -  h, y - h), new< Size(3 * h, 3 *h));
Bitmap CroppedImage = CropImage(Bitmapsource, section);

The cropped image function code is:

public Bitmap CropImage(Bitmap source, Rectangle section)  {
Bitmap bmp = new Bitmap(section.Width, section.Height);
Graphics g = Graphics.FromImage(bmp);
 g.DrawImage(source, 0, 0, section, GraphicsUnit.Pixel);
  return bmp;}

Hope that will help for any eyeball or pupil extraction code.

Points of Interest

For face recognition or detection, eye recognition can be helpful.

History

  • 22nd December, 2010: Initial post
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