Asp.Net 动态生成验证码

12/14/2009来源:ASP.NET技巧人气:9754

我们在设计用户登录模块时,经常会用到验证码,可以有效地防止黑客软件的恶意破解,现公开我常用的验证码的源代码,
   使用方法:
   1、在Web项目中添加一个类,如“CreateImage.cs”,然后将我公布的源代码Copy进去;
   2、再新建一个Web窗体,如“Image.aspx”,在Page_Load中加入代码 “CreateImage.DrawImage ();”当然别忘了加上对类的引用哦!!
   3、在页面的合适位置上(你想放验证码的位置)上加上如下javascript代码就OK 了,
  
  
  源代码如下:   
  ///
  /// 验证码模块
  ///
  public class CreateImage
  {
  public static void DrawImage()
  {
  CreateImage img=new CreateImage();
  HttpContext.Current.session["CheckCode"]=img.RndNum(4);
  img.CreateImages(HttpContext.Current.Session["CheckCode"].ToString());
  }
  
  ///
  /// 生成验证图片
  ///
  /// 验证字符
  PRivate void CreateImages(string checkCode)
  {
  int iwidth = (int)(checkCode.Length * 13);
  System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 23);
  Graphics g = Graphics.FromImage(image);
  g.Clear(Color.White);
  //定义颜色
  Color[] c = {Color.Black,Color.Red,Color.DarkBlue,Color.Green,Color.Orange,Color.Brown,Color.DarkCyan,Color.Purple};
  //定义字体
  string[] font = {"Verdana","Microsoft Sans Serif","Comic Sans MS","Arial","宋体"};
  Random rand = new Random();
  //随机输出噪点
  for(int i=0;i<50;i++)
  {
  int x = rand.Next(image.Width);
  int y = rand.Next(image.Height);
  g.DrawRectangle(new Pen(Color.LightGray, 0),x,y,1,1);
  }
  
  //输出不同字体和颜色的验证码字符
  for(int i=0;i
  {
  int cindex = rand.Next(7);
  int findex = rand.Next(5);
  
  Font f = new System.Drawing.Font(font[findex], 10, System.Drawing.FontStyle.Bold);
  Brush b = new System.Drawing.SolidBrush(c[cindex]);
  int ii=4;
  if((i+1)%2==0)
  {
  ii=2;
  }
  g.DrawString(checkCode.Substring(i,1), f, b, 3+(i*12), ii);
  }
  //画一个边框
  g.DrawRectangle(new Pen(Color.Black,0),0,0,image.Width-1,image.Height-1);
  
  //输出到浏览器
  System.IO.MemoryStream ms = new System.IO.MemoryStream();
  image.Save(ms,System.Drawing.Imaging.ImageFormat.Jpeg);
  HttpContext.Current.Response.ClearContent();
  //Response.ClearContent();
  HttpContext.Current.Response.ContentType = "image/Jpeg";
  HttpContext.Current.Response.BinaryWrite(ms.ToArray());
  g.Dispose();
  image.Dispose();
  }
  
  ///
  /// 生成随机的字母
  ///
  /// 生成字母的个数
  /// string
  private string RndNum(int VcodeNum)
  {
  string Vchar = "0,1,2,3,4,5,6,7,8,9" ;
  string[] VcArray = Vchar.Split(',') ;
  string VNum = "" ; //由于字符串很短,就不用StringBuilder了
  int temp = -1 ; //记录上次随机数值,尽量避免生产几个一样的随机数
  
  //采用一个简单的算法以保证生成随机数的不同
  Random rand =new Random();
  for ( int i = 1 ; i < VcodeNum+1 ; i++ )
  {
  if ( temp != -1)
  {
  rand =new Random(i*temp*unchecked((int)DateTime.Now.Ticks));
  }
  int t = rand.Next(VcArray.Length ) ;
  if (temp != -1 && temp == t)
  {
  return RndNum( VcodeNum );
  }
  temp = t ;
  VNum += VcArray[t];
  }
  return VNum ;
  }
  }