绘制验证码

 1     ///*************************************************
 2     /// 函数:GenerateCheckCode:生成四位随机数
 3     ///      CreateCheckCodeImg:绘制验证码
 4     /// 作者:王洪剑
 5     /// 日期:2009-6-9
 6     ///*************************************************
 7     //生成随机数
 8     private string GenerateCheckCode()
 9     {
10         int intNum;
11         char chrCode;
12         string strCheckCode = String.Empty;
13         Random random = new Random();
14         for (int i = 0; i < 4; i++)
15         {
16             intNum = random.Next();
17             if (intNum % 2 == 0)
18                 chrCode = (char)('1' + (char)(intNum % 10));
19             else
20                 chrCode = (char)('A' + (char)(intNum % 26));
21             strCheckCode += chrCode.ToString();
22         }
23         Session["HopeCheckCode"] = strCheckCode.ToString();
24         return strCheckCode.ToString();
25     }
26 
27     //绘制验证码
28     private void CreateCheckCodeImg(string strCheckCode)
29     {
30         if (strCheckCode == null || strCheckCode.Trim() == String.Empty)
31             return;
32         System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((strCheckCode.Length * 10.5)), 20);
33         Graphics gr = Graphics.FromImage(image);
34         try
35         {
36             Random random = new Random();//生成随机生成器
37             gr.Clear(Color.Transparent);//清空背景色并绘制白色
38             //画图片的背景噪音线
39             for (int i = 0; i < 2; i++)
40             {
41                 int x1 = random.Next(image.Width);
42                 int x2 = random.Next(image.Width);
43                 int y1 = random.Next(image.Height);
44                 int y2 = random.Next(image.Height);
45                 gr.DrawLine(new Pen(Color.Green), x1, x2, y1, y2);
46                 Font font = new System.Drawing.Font("Times New Roman", 12, (System.Drawing.FontStyle.Bold));//字体
47                 System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);//笔刷渐变色
48                 gr.DrawString(strCheckCode, font, brush, 2, 2);
49             }
50 
51             //画图片前景噪音点
52             for (int i = 0; i < 30; i++)
53             {
54                 int x = random.Next(image.Width);
55                 int y = random.Next(image.Height);
56                 image.SetPixel(x, y, Color.FromArgb(random.Next()));
57             }
58             //画边框线
59             gr.DrawRectangle(new Pen(Color.Transparent), 0, 0, image.Width - 1, image.Height - 1);
60             System.IO.MemoryStream ms = new System.IO.MemoryStream();
61             image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);//生成图片格式
62             Response.ClearContent();
63             Response.ContentType = "image/Png";
64             Response.BinaryWrite(ms.ToArray());
65 
66         }
67         catch (Exception ex)
68         { Response.Write("生成验证码失败:" + ex.Message); }
69     }
70