C# winform登陆框验证码的实现方法

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Drawing;
using System.Drawing.Drawing2D;

 

namespace BigHorseLib.Security

{

  public class ValidCode

  {

    #region Private Fields
    private const double PI = 3.1415926535897932384626433832795;
    private const double PI2 = 6.283185307179586476925286766559;
    //private readonly int _wordsLen = 4;
    private int _len;
    private CodeType _codetype;
    private readonly Single _jianju = (float )18.0;
    private readonly Single _height = (float )24.0;
    private string _checkCode;
    #endregion
    #region Public Property
    public string CheckCode

    {

      get

      {

        return _checkCode;

      }

    }

    #endregion
    #region Constructors
    /// <summary>
    /// public constructors
    /// </summary>
    /// <param name="len"> 验证码长度 </param>
    /// <param name="ctype"> 验证码类型：字母、数字、字母+ 数字 </param>

    public ValidCode(int len, CodeType ctype)

    {

      this ._len = len;

      this ._codetype = ctype;

    }

    #endregion
    #region Public Field
     public enum CodeType {Words, Numbers, Characters, Alphas }
    #endregion
    #region Private Methods

 

    private string GenerateNumbers()
    {

      string strOut = "" ;

      System.Random random = new Random ();

       for (int i = 0; i < _len; i++)

      {

        string num = Convert .ToString(random.Next(10000)%10);
        strOut += num;
      }
      return strOut.Trim();

    }

 

    private string GenerateCharacters()
    {

      string strOut = "" ;

      System.Random random = new Random ();

      for (int i = 0; i < _len; i++)

      {

        string num = Convert .ToString((char )(65+random.Next(10000)%26));

        strOut += num;

      }

      return strOut.Trim();
    }
    //

    private string GenerateAlphas()
    {

      string strOut = "" ;
      string num = "" ;
      System.Random random = new Random ();

      for (int i = 0; i < _len; i++)

      {

        if (random.Next(500) % 2 == 0)

        {

          num = Convert .ToString(random.Next(10000) % 10);

        }

        else

        {

          num = Convert .ToString((char )(65 + random.Next(10000) % 26));

        }

        strOut += num;

      }

      return strOut.Trim();

    }

 

    private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
    {

      System.Drawing.Bitmap destBmp = new Bitmap (srcBmp.Width, srcBmp.Height);
 
      // 将位图背景填充为白色
      System.Drawing.Graphics graph = System.Drawing.Graphics .FromImage(destBmp);
      graph.FillRectangle(new SolidBrush (System.Drawing.Color .White), 0, 0, destBmp.Width, destBmp.Height);
      graph.Dispose();
      double dBaseAxisLen = bXDir ? (double )destBmp.Height : (double )destBmp.Width;
      for (int i = 0; i < destBmp.Width; i++)
       {

        for (int j = 0; j < destBmp.Height; j++)

        {

          double dx = 0;
          dx = bXDir ? (PI2 * (double )j) / dBaseAxisLen : (PI2 * (double )i) / dBaseAxisLen;
          dx += dPhase;
          double dy = Math .Sin(dx);
 

          // 取得当前点的颜色
          int nOldX = 0, nOldY = 0;
          nOldX = bXDir ? i + (int )(dy * dMultValue) : i;
          nOldY = bXDir ? j : j + (int )(dy * dMultValue);

          System.Drawing.Color color = srcBmp.GetPixel(i, j);
          if (nOldX >= 0 && nOldX < destBmp.Width

           && nOldY >= 0 && nOldY < destBmp.Height)

          {

            destBmp.SetPixel(nOldX, nOldY, color);

          }

        }

      }

 

      return destBmp;

    }

    #endregion

    #region Public Methods
    public Stream CreateCheckCodeImage()
    {

      string checkCode;
      switch (_codetype){
        case CodeType .Alphas:
          checkCode = GenerateAlphas();
          break ;
        case CodeType .Numbers:
          checkCode = GenerateNumbers();
           break ;

        case CodeType .Characters:
          checkCode = GenerateCharacters();
          break ;
        default :
          checkCode = GenerateAlphas();

          break ;

      }

       this ._checkCode = checkCode;
      MemoryStream ms = null ;
      //
      if (checkCode == null || checkCode.Trim() == String .Empty)

        return null ;

      Bitmap image = new System.Drawing.Bitmap ((int )Math .Ceiling((checkCode.Length * _jianju)), (int )_height);

      Graphics g = Graphics .FromImage(image);

      try

      {

        Random random = new Random ();

        g.Clear(Color .White);

        // 画图片的背景噪音线

        for (int i = 0; i < 18; 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 .FromArgb(random.Next()),1), x1, y1, x2, y2);
        }
        Font font = new System.Drawing.Font ("Times New Roman" , 14, System.Drawing.FontStyle .Bold);
        LinearGradientBrush brush = new LinearGradientBrush (new Rectangle (0, 0, image.Width, image.Height), Color .Blue, Color .DarkRed, 1.2f, true );

        if (_codetype != CodeType .Words)
        {
          for (int i = 0; i < checkCode.Length; i++)

          {

            g.DrawString(checkCode.Substring(i, 1), font, brush, 2 + i * _jianju, 1);

          }

        }else {

          g.DrawString(checkCode, font, brush, 2, 2);

        }

        // 画图片的前景噪音点

        for (int i = 0; i < 150; i++)

        {
          int x = random.Next(image.Width);
          int y = random.Next(image.Height);
          image.SetPixel(x, y, Color .FromArgb(random.Next()));

        }

        // 画图片的波形滤镜效果

        if (_codetype != CodeType .Words)

        {

          image = TwistImage(image, true , 3, 1);

        }

        // 画图片的边框线

        g.DrawRectangle(new Pen (Color .Silver), 0, 0, image.Width - 1, image.Height - 1);

 

        ms = new System.IO.MemoryStream ();

        image.Save(ms, System.Drawing.Imaging.ImageFormat .Gif);

      }

      finally

      {

        g.Dispose();

        image.Dispose();

      }

      return ms;

    }

    #endregion

  }

}

 

// 图片加载验证码
picValidCode.Image = Bitmap .FromStream(validCode.CreateCheckCodeImage())

// 验证
  if (!this .txtValidCode.Text.Equals(_validCode.CheckCode))

   {

     MessageBox .Show(" 请输入正确的验证码!" , this .Text);

     this .txtValidCode.Focus();

     return ;

 }