ASP.NET inspired by 12306 dynamic verification code implements dynamic GIF verification code

public void ShowCode()
   {
     //对象实例化
     Validate GifValidate = new Validate();
 
     #region 对验证码进行设置(不进行设置时,将以默认值生成)
     //验证码位数，不小于4位
     GifValidate.ValidateCodeCount = 4;
     //验证码字体型号(默认13)
     GifValidate.ValidateCodeSize = 13;
     //验证码图片高度,高度越大,字符的上下偏移量就越明显
     GifValidate.ImageHeight = 23;
     //验证码字符及线条颜色(需要参考颜色类)
     GifValidate.DrawColor = System.Drawing.Color.BlueViolet;
     //验证码字体(需要填写服务器安装的字体)
     GifValidate.ValidateCodeFont = "Arial";
     //验证码字符是否消除锯齿
     GifValidate.FontTextRenderingHint = false;
     //定义验证码中所有的字符(","分离),似乎暂时不支持中文
     GifValidate.AllChar = "1,2,3,4,5,6,7,8,9,0,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
     #endregion
 
     //输出图像(Session名称)
     GifValidate.OutPutValidate("GetCode");
   }

public class Validate
  {
    public string AllChar = "1,2,3,4,5,6,7,8,9,0,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
    public Color DrawColor = Color.BlueViolet;
    public bool FontTextRenderingHint = false;
    public int ImageHeight = 0x17;
    private byte TrueValidateCodeCount = 4;
    protected string ValidateCode = "";
    public string ValidateCodeFont = "Arial";
    public float ValidateCodeSize = 13f;
 
    private void CreateImageBmp(out Bitmap ImageFrame)
    {
      char[] chArray = this.ValidateCode.ToCharArray(0, this.ValidateCodeCount);
      int width = (int) (((this.TrueValidateCodeCount * this.ValidateCodeSize) * 1.3) + 4.0);
      ImageFrame = new Bitmap(width, this.ImageHeight);
      Graphics graphics = Graphics.FromImage(ImageFrame);
      graphics.Clear(Color.White);
      Font font = new Font(this.ValidateCodeFont, this.ValidateCodeSize, FontStyle.Bold);
      Brush brush = new SolidBrush(this.DrawColor);
      int maxValue = (int) Math.Max((float) ((this.ImageHeight - this.ValidateCodeSize) - 3f), (float) 2f);
      Random random = new Random();
      for (int i = 0; i < this.TrueValidateCodeCount; i++)
      {
        int[] numArray = new int[] { (((int) (i * this.ValidateCodeSize)) + random.Next(1)) + 3, random.Next(maxValue) };
        Point point = new Point(numArray[0], numArray[1]);
        if (this.FontTextRenderingHint)
        {
          graphics.TextRenderingHint = TextRenderingHint.SingleBitPerPixel;
        }
        else
        {
          graphics.TextRenderingHint = TextRenderingHint.AntiAlias;
        }
        graphics.DrawString(chArray[i].ToString(), font, brush, (PointF) point);
      }
      graphics.Dispose();
    }
 
    private void CreateImageGif()
    {
      AnimatedGifEncoder encoder = new AnimatedGifEncoder();
      MemoryStream stream = new MemoryStream();
      encoder.Start();
      encoder.SetDelay(5);
      encoder.SetRepeat(0);
      for (int i = 0; i < 10; i++)
      {
        Bitmap bitmap;
        this.CreateImageBmp(out bitmap);
        this.DisposeImageBmp(ref bitmap);
        bitmap.Save(stream, ImageFormat.Png);
        encoder.AddFrame(Image.FromStream(stream));
        stream = new MemoryStream();
      }
      encoder.OutPut(ref stream);
      HttpContext.Current.Response.ClearContent();
      HttpContext.Current.Response.ContentType = "image/Gif";
      HttpContext.Current.Response.BinaryWrite(stream.ToArray());
      stream.Close();
      stream.Dispose();
    }
 
    private void CreateValidate()
    {
      this.ValidateCode = "";
      string[] strArray = this.AllChar.Split(new char[] { &#39;,&#39; });
      int index = -1;
      Random random = new Random();
      for (int i = 0; i < this.ValidateCodeCount; i++)
      {
        if (index != -1)
        {
          random = new Random((i * index) * ((int) DateTime.Now.Ticks));
        }
        int num3 = random.Next(0x23);
        if (index == num3)
        {
          this.CreateValidate();
        }
        index = num3;
        this.ValidateCode = this.ValidateCode + strArray[index];
      }
      if (this.ValidateCode.Length > this.TrueValidateCodeCount)
      {
        this.ValidateCode = this.ValidateCode.Remove(this.TrueValidateCodeCount);
      }
    }
 
    private void DisposeImageBmp(ref Bitmap ImageFrame)
    {
      Graphics graphics = Graphics.FromImage(ImageFrame);
      Pen pen = new Pen(this.DrawColor, 1f);
      Random random = new Random();
      Point[] pointArray = new Point[2];
      for (int i = 0; i < 15; i++)
      {
        pointArray[0] = new Point(random.Next(ImageFrame.Width), random.Next(ImageFrame.Height));
        pointArray[1] = new Point(random.Next(ImageFrame.Width), random.Next(ImageFrame.Height));
        graphics.DrawLine(pen, pointArray[0], pointArray[1]);
      }
      graphics.Dispose();
    }
 
    public void OutPutValidate(string ValidateCodeSession)
    {
      this.CreateValidate();
      this.CreateImageGif();
      HttpContext.Current.Session[ValidateCodeSession] = this.ValidateCode;
    }
 
    public byte ValidateCodeCount
    {
      get
      {
        return this.TrueValidateCodeCount;
      }
      set
      {
        if (value > 4)
        {
          this.TrueValidateCodeCount = value;
        }
      }
    }
  }