如何编写ASP.NET实现动态GIF验证码

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实现方法：

 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");    }

调用主要方法：

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[] { ',' });      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;        }      }    }  }

验证码效果：

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