Automatic pupil detection and extraction by c#

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

coding steps

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 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 croppedimage 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