c#图片验证码

  1 using System;
  2 using System.Drawing;
  3 namespace cxyy.Web
  4 {
  5     public partial class ValidateCode : System.Web.UI.Page
  6     {
  7         private void Page_Load(object sender, System.EventArgs e)
  8         {
  9             string checkCode = GetRandomCode(4);
 10             Session["CheckCode"] = checkCode;
 11             SetPageNoCache();
 12             CreateImage(checkCode);
 13         }
 14 
 15         /// <summary>
 16         /// 设置页面不被缓存
 17         /// </summary>
 18         private void SetPageNoCache()
 19         {
 20             Response.Buffer = true;
 21             Response.ExpiresAbsolute = System.DateTime.Now.AddSeconds(-1);
 22             Response.Expires = 0;
 23             Response.CacheControl = "no-cache";
 24             Response.AppendHeader("Pragma", "No-Cache");
 25         }
 26 
 27         private string CreateRandomCode(int codeCount)
 28         {
 29             string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,i,J,K,M,N,P,Q,R,S,T,U,W,X,Y,Z";
 30             string[] allCharArray = allChar.Split(',');
 31             string randomCode = "";
 32             int temp = -1;
 33 
 34             Random rand = new Random();
 35             for (int i = 0; i < codeCount; i++)
 36             {
 37                 if (temp != -1)
 38                 {
 39                     rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
 40                 }
 41                 int t = rand.Next(35);
 42                 if (temp == t)
 43                 {
 44                     return CreateRandomCode(codeCount);//性能问题
 45                 }
 46                 temp = t;
 47                 randomCode += allCharArray[t];
 48             }
 49             return randomCode;
 50         }
 51         private string GetRandomCode(int CodeCount)
 52         {
 53             string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,i,J,K,M,N,P,Q,R,S,T,U,W,X,Y,Z";
 54             string[] allCharArray = allChar.Split(',');
 55             string RandomCode = "";
 56             int temp = -1;
 57 
 58             Random rand = new Random();
 59             for (int i = 0; i < CodeCount; i++)
 60             {
 61                 if (temp != -1)
 62                 {
 63                     rand = new Random(temp * i * ((int)DateTime.Now.Ticks));
 64                 }
 65 
 66                 int t = rand.Next(33);
 67 
 68                 while (temp == t)
 69                 {
 70                     t = rand.Next(33);
 71                 }
 72 
 73                 temp = t;
 74                 RandomCode += allCharArray[t];
 75             }
 76 
 77             return RandomCode;
 78         }
 79         private void CreateImage(string checkCode)
 80         {
 81             int iwidth = (int)(checkCode.Length * 14);
 82             System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
 83             Graphics g = Graphics.FromImage(image);
 84             Font f = new System.Drawing.Font("Arial ", 10, System.Drawing.FontStyle.Bold);
 85             Brush b = new System.Drawing.SolidBrush(Color.FromArgb(255,255,255));
 86             Brush r = new System.Drawing.SolidBrush(Color.FromArgb(255,0,0));
 87 
 88             //g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
 89             //g.Clear(Color.AliceBlue);//背景色
 90             g.Clear(System.Drawing.ColorTranslator.FromHtml("#FD8BA6"));//背景色
 91 
 92             char[] ch = checkCode.ToCharArray();
 93             for (int i = 0; i < ch.Length; i++)
 94             {
 95                 if (ch[i] >= '0' && ch[i] <= '9')
 96                 {
 97                     //数字用红色显示
 98                     g.DrawString(ch[i].ToString(), f, r, 3 + (i * 12), 3);
 99                 }
100                 else
101                 {   //字母用黑色显示
102                     g.DrawString(ch[i].ToString(), f, b, 3 + (i * 12), 3);
103                 }
104             }
105 
106             //for循环用来生成一些随机的水平线
107             //            Pen blackPen = new Pen(Color.Black, 0);
108             //            Random rand = new Random();
109             //            for (int i=0;i<5;i++)
110             //            {
111             //                int y = rand.Next(image.Height);
112             //                g.DrawLine(blackPen,0,y,image.Width,y);
113             //            }
114 
115             System.IO.MemoryStream ms = new System.IO.MemoryStream();
116             image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
117             //history back 不重复 
118             Response.Cache.SetNoStore();//这一句         
119             Response.ClearContent();
120             Response.ContentType = "image/Jpeg";
121             Response.BinaryWrite(ms.ToArray());
122             g.Dispose();
123             image.Dispose();
124         }        
125     }
126 }
127