Web服务实现验证码

Service1.asmx
using System.Drawing;
  [WebMethod]
  public byte[] GenerateImage(int nLen,ref string strKey){
   int nBmpWidth=13*nLen+5;
   int nBmpHeight=25;
   System.Drawing.Bitmap bmp=new System.Drawing.Bitmap (nBmpWidth,nBmpHeight);
   //1.生成随机图像背景颜色
   int nRed,nGreen,nBlue;
   System.Random rd=new Random((int)System.DateTime.Now.Ticks);
   nRed=rd.Next(255)%128+128;
   nGreen=rd.Next(255)%128+128;
   nBlue=rd.Next(255)%128+128;
   //2.填充位图背景
   System.Drawing.Graphics graph=System.Drawing.Graphics.FromImage(bmp);
   graph.FillRectangle(new SolidBrush(System.Drawing.Color.FromArgb(nRed,nGreen,nBlue))
    ,0
    ,0
    ,nBmpWidth
    ,nBmpHeight);
   //3.图片的背景噪音线
   int nLines=10;
   System.Drawing.Pen pen=new System.Drawing.Pen(System.Drawing.Color.FromArgb(nRed-17,nGreen-17,nBlue-17),2);
   for(int a=0;a<nLines;a++){
    int x1=rd.Next()%nBmpWidth;
    int y1=rd.Next()%nBmpHeight;
    int x2=rd.Next()%nBmpWidth;
    int y2=rd.Next()%nBmpHeight;
    graph.DrawLine(pen,x1,y1,x2,y2);
   }
   //采用的字符集，可以随意拓展
   string strCode="ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
   //4.循环获得字符，并绘制
   string strResult="";
   for(int i=0;i<nLen;i++){
    int x=(i*13+rd.Next(3));
    int y=rd.Next(4)+1;
    //确定字体
    System.Drawing.Font font=new System.Drawing.Font ("arial",12+rd.Next()%4,System.Drawing.FontStyle.Bold);
    char c=strCode[rd.Next(strCode.Length)];//随机获取字符
    strResult +=c.ToString();
    //绘制字符
    graph.DrawString(c.ToString(),font,new SolidBrush(System.Drawing.Color.FromArgb(nRed-60,nGreen-60+y*3,nBlue-40+y*3)),x,y);
   }
   //图画片的前景噪音点
   for(int i=0;i<10;i++){
    int x=rd.Next(bmp.Width);
    int y=rd.Next(bmp.Height);
    bmp.SetPixel(x,y,Color.FromArgb(rd.Next()));
   }
   //图画片的边框线
   graph.DrawRectangle(new Pen(Color.Silver),0,0,bmp.Width-1,bmp.Height-1);
   //输出
   System.IO.MemoryStream bstream=new System.IO.MemoryStream ();
   bmp.Save(bstream,System.Drawing.Imaging.ImageFormat.Jpeg);
   bmp.Dispose();
   graph.Dispose();
   strKey=strResult;
   byte[] byteReturn=bstream.ToArray();
   bstream.Close();
   return byteReturn;
  }
gif.aspx
  private void Page_Load(object sender, System.EventArgs e)
  {
   GenerateImage.Service1 imgsvr=new WebImage.GenerateImage.Service1();
   string strKey = "";
   byte[] data = imgsvr.GenerateImage(6,ref strKey);
   Session["regcode"] = strKey;
   Response.OutputStream.Write(data,0,data.Length);
  }

Main.aspx
  private void btLogin_Click(object sender, System.EventArgs e)
  {
   if(this.tbCode.Text!=Session["regcode"].ToString())
    Response.Write("注册码错误！");
  }