asp.net 生成图片验证码

1 protected void Page_Load(object sender, EventArgs e)
2     {
3         string tmp = RndNum(4);
4         HttpCookie a = new HttpCookie("ImageV", tmp);
5         Response.Cookies.Add(a);
6         this.ValidateCode(tmp);
7     }
8     private void ValidateCode(string VNum)
9     {
10         Bitmap Img = null;
11         Graphics g = null;
12         MemoryStream ms = null;
13
14         int gheight = VNum.Length * 12;
15         Img = new Bitmap(gheight, 25);
16         g = Graphics.FromImage(Img);
17         //背景颜色
18         g.Clear(Color.LightSteelBlue);
19         //文字字体
20         Font f = new Font("Arial Black", 10);
21         //文字颜色
22         SolidBrush s = new SolidBrush(Color.RoyalBlue);
23         g.DrawString(VNum, f, s, 3, 3);
24         ms = new MemoryStream();
25         Img.Save(ms, ImageFormat.Jpeg);
26         Response.ClearContent();
27         Response.ContentType = "images/Jpeg";
28         Response.BinaryWrite(ms.ToArray());
29         g.Dispose();
30         Img.Dispose();
31         Response.End();
32     }
33
34     private string RndNum(int VcodeNum)
35     {
36         string Vchar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p" +
37         ",q,r,s,t,u,v,w,x,y,z";
38         string[] VcArray = Vchar.Split(new Char[] { ',' });
39         string VNum = "";
40         int temp = -1;
41
42         Random rand = new Random();
43
44         for (int i = 1; i < VcodeNum + 1; i++)
45         {
46             if (temp != -1)
47             {
48                 rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
49             }
50
51             int t = rand.Next(35);
52             if (temp != -1 && temp == t)
53             {
54                 return RndNum(VcodeNum);
55             }
56             temp = t;
57             VNum += VcArray[t];
58         }
59         return VNum;
60     }