验证码收集

带曲线的验证码
转自：http://www.cnblogs.com/liudao/archive/2007/04/29/732065.html
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/// <summary>
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/// 正弦曲线Wave扭曲图片（Edit By 51aspx.com）
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/// </summary>
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/// <param name="srcBmp">图片路径</param>
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/// <param name="bXDir">如果扭曲则选择为True</param>
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/// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param>
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/// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param>
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/// <returns></returns>
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public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
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{
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System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
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// 将位图背景填充为白色
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System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
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graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
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graph.Dispose();
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double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;
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for (int i = 0; i < destBmp.Width; i++)
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{
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for (int j = 0; j < destBmp.Height; j++)
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{
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double dx = 0;
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dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
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dx += dPhase;
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double dy = Math.Sin(dx);
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// 取得当前点的颜色
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int nOldX = 0, nOldY = 0;
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nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
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nOldY = bXDir ? j : j + (int)(dy * dMultValue);
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System.Drawing.Color color = srcBmp.GetPixel(i, j);
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if (nOldX >= 0 && nOldX < destBmp.Width
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&& nOldY >= 0 && nOldY < destBmp.Height)
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{
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destBmp.SetPixel(nOldX, nOldY, color);
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}
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}
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}
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return destBmp;
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        }

普通的验证码
转自：http://www.cnblogs.com/gwazy/archive/2005/04/18/139510.html

public class ValidateCode : System.Web.UI.Page
{
  private void Page_Load(object sender, System.EventArgs e)
  {
   this.CreateCheckCodeImage(GenerateCheckCode());
  }

  #region Web 窗体设计器生成的代码
  override protected void OnInit(EventArgs e)
  {
   //
   // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
   //
   InitializeComponent();
   base.OnInit(e);
  }

  /// <summary>
  /// 设计器支持所需的方法 - 不要使用代码编辑器修改
  /// 此方法的内容。
  /// </summary>
  private void InitializeComponent()
  {
   this.Load += new System.EventHandler(this.Page_Load);
  }
  #endregion

  private string GenerateCheckCode()
  {
   int number;
   char code;
   string checkCode = String.Empty;

System.Random random = new Random();

   for(int i=0; i<5; i++)
   {
    number = random.Next();

    if(number % 2 == 0)
     code = (char)('0' + (char)(number % 10));
    else
     code = (char)('A' + (char)(number % 26));

checkCode += code.ToString();
}

Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

return checkCode;
}

  private void CreateCheckCodeImage(string checkCode)
  {
   if(checkCode == null || checkCode.Trim() == String.Empty)
    return;

System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
Graphics g = Graphics.FromImage(image);

   try
   {
    //生成随机生成器
    Random random = new Random();

//清空图片背景色
g.Clear(Color.White);

    //画图片的背景噪音线
    for(int i=0; i<25; i++)
    {
     int x1 = random.Next(image.Width);
     int x2 = random.Next(image.Width);
     int y1 = random.Next(image.Height);
     int y2 = random.Next(image.Height);

g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
}

    Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
    System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
    g.DrawString(checkCode, font, brush, 2, 2);

    //画图片的前景噪音点
    for(int i=0; i<100; i++)
    {
     int x = random.Next(image.Width);
     int y = random.Next(image.Height);

image.SetPixel(x, y, Color.FromArgb(random.Next()));
}

//画图片的边框线
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

    System.IO.MemoryStream ms = new System.IO.MemoryStream();
    image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
    Response.ClearContent();
    Response.ContentType = "image/Gif";
    Response.BinaryWrite(ms.ToArray());
   }
   finally
   {
    g.Dispose();
    image.Dispose();
   }
  }
}

给同是菜鸟的几个注释：
1引用时直接引用前台页就可以了；（例：checkcode.aspx）
2别忘了在命名空间中加上：“using System.Drawing;”
3如果想刷新的话就：<img id="XXXX" src="XXXX.aspx?" alt="看不清？点击更换" onclick="this.src=this.src+'?'" />