ASP.NET画验证码

  1 protected void Page_Load(object sender, EventArgs e)
  2 
  3     {
  4 
  5         CreateCheckCodeImage(GenerateCheckCode());
  6 
  7     }
  8 
  9  
 10 
 11     private string GenerateCheckCode()
 12 
 13     {
 14 
 15         int number;
 16 
 17         char code;
 18 
 19         string checkCode = String.Empty;
 20 
 21         System.Random random = new Random();
 22 
 23  
 24 
 25         for (int i = 0; i < 4; i++)
 26 
 27         {
 28 
 29             number = random.Next();
 30 
 31  
 32 
 33             if (number % 2 == 0)
 34 
 35                 code = (char)('0' + (char)(number % 10));
 36 
 37             else
 38 
 39                 code = (char)('A' + (char)(number % 26));
 40 
 41  
 42 
 43             checkCode += code.ToString();
 44 
 45         }
 46 
 47         Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
 48 
 49         return checkCode;
 50 
 51     }
 52 
 53  
 54 
 55     private void CreateCheckCodeImage(string checkCode)
 56 
 57     {
 58 
 59         if (checkCode == null || checkCode.Trim() == String.Empty)
 60 
 61             return;
 62 
 63         System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
 64 
 65         Graphics g = Graphics.FromImage(image);
 66 
 67         try
 68 
 69         {
 70 
 71             //生成随机生成器
 72 
 73             Random random = new Random();
 74 
 75             //清空图片背景色
 76 
 77             g.Clear(Color.White);
 78 
 79             //画图片的背景噪音线
 80 
 81             for (int i = 0; i < 2; i++)
 82 
 83             {
 84 
 85                 int x1 = random.Next(image.Width);
 86 
 87                 int x2 = random.Next(image.Width);
 88 
 89                 int y1 = random.Next(image.Height);
 90 
 91                 int y2 = random.Next(image.Height);
 92 
 93                 g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);
 94 
 95             }
 96 
 97             Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
 98 
 99             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);
100 
101             g.DrawString(checkCode, font, brush, 2, 2);
102 
103             //画图片的前景噪音点
104 
105             for (int i = 0; i < 100; i++)
106 
107             {
108 
109                 int x = random.Next(image.Width);
110 
111                 int y = random.Next(image.Height);
112 
113                 image.SetPixel(x, y, Color.FromArgb(random.Next()));
114 
115             }
116 
117             //画图片的边框线
118 
119             g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
120 
121             System.IO.MemoryStream ms = new System.IO.MemoryStream();
122 
123             image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
124 
125             Response.ClearContent();
126 
127             Response.ContentType = "image/Gif";
128 
129             Response.BinaryWrite(ms.ToArray());
130 
131         }
132 
133         finally
134 
135         {
136 
137             g.Dispose();
138 
139             image.Dispose();
140 
141         }
142 
143 }

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原文地址：https://www.cnblogs.com/it-bobo/p/3860738.html