public Bitmap CreateCaptcha()
    {
      Random       randomGenerator = new Random();
      //                        Bitmap       bmp = new Bitmap(img_width, img_height, PixelFormat.Format16bppRgb555);
      Bitmap       bmp = new Bitmap(img_width, img_height, PixelFormat.Format32bppArgb);
      Rectangle    rect = new Rectangle(0, 0, img_width, img_height);
      StringFormat format = new StringFormat();
      Graphics     g = Graphics.FromImage(bmp);      

      format.Alignment = StringAlignment.Center;
      format.LineAlignment = StringAlignment.Center;

      SizeF        size;
      float        fontSize = img_fontsize + 1;
      Font         font;                

      try {
        font = new Font(img_fontname, img_fontsize);
        font.Dispose();
      }
      catch (Exception ex) {
        img_fontname = System.Drawing.FontFamily.GenericSerif.Name;
      }
                        
      // build a new string with space through the chars
      // i.e. keyword 'hello' become 'h e l l o '
      string tempKey = "";                      

      for (int ii=0; ii< keyword.Length; ii++)
      {
        tempKey = String.Concat(tempKey, keyword[ii].ToString());
        tempKey = String.Concat(tempKey, " ");
      }

      // Adjust the font size until the text fits within the image.
      do {
        fontSize--;
        font = new Font(img_fontname, fontSize, img_fontstyle);
        size = g.MeasureString(tempKey, font);
      } while (size.Width > (0.8*bmp.Width));

      img_font = font;

      g.Clear(Color.Silver);
      g.SmoothingMode = SmoothingMode.AntiAlias;

      // fill with a liner gradient
      // random colors
      g.FillRectangle(new LinearGradientBrush(new Point(0,0), new Point(bmp.Width,bmp.Height), 
                                              Color.FromArgb(255, //randomGenerator.Next(255),
                                                             randomGenerator.Next(255),
                                                             randomGenerator.Next(255),
                                                             randomGenerator.Next(255)),
                                              Color.FromArgb(randomGenerator.Next(100),
                                                             randomGenerator.Next(255),
                                                             randomGenerator.Next(255),
                                                             randomGenerator.Next(255))), rect);
      if (degree == 0)
        BitmapFilter.Swirl(bmp, randomGenerator.NextDouble(), true);
      else
        BitmapFilter.Swirl(bmp, degree , true);

      HatchBrush hatchBrush = new HatchBrush(HatchStyle.LargeConfetti, Color.LightGray, Color.DarkGray);

      int m = Math.Max(rect.Width, rect.Height);
      for (int i = 0; i < (int) (rect.Width * rect.Height / 30F); i++) {
        int x = randomGenerator.Next(rect.Width);
        int y = randomGenerator.Next(rect.Height);
        int w = randomGenerator.Next(m / 50);
        int h = randomGenerator.Next(m / 50);
        g.FillEllipse(hatchBrush, x, y, w, h);
      }

      int posy;
      int posx = Convert.ToInt32((img_width - size.Width)/2);
      int deltax = Convert.ToInt32(size.Width/tempKey.Length);
        
      Point[] ps = new Point[points];
                        
      for (int ii=0; ii < points; ii++) {
        int x,y;
        x = randomGenerator.Next(bmp.Width);
        y = randomGenerator.Next(bmp.Height);
        ps[ii] = new Point(x,y);
      }
      g.DrawCurve(new Pen( img_linecolor, 2), ps, Convert.ToSingle(randomGenerator.NextDouble()));

      for (int l=0; l < tempKey.Length; l++ ) {
        posy = ((int)(2.5 * (bmp.Height/5))) + (((l%2)==0)?-2:2) * ((int)(size.Height/3));
        posy = (int)((bmp.Height/2)+ (size.Height/2));
        posy += (int) ((((l%2)==0)?-2:2) * ((size.Height/3)));
        posx += deltax;
        g.DrawString(tempKey[l].ToString(), img_font, img_fontcolor, posx, posy, format);
      }
      //BitmapFilter.Water(bmp, wave, true);
      //BitmapFilter.TimeWarp(bmp, 2, true);
                        
      font.Dispose();
      hatchBrush.Dispose();
      g.Dispose();

      return bmp;
    }