生成图片验证码，防止软件识别

图片生成与随机数生成函数 /// <summary> /// 生成随机码 /// </summary> /// <param name="length">随机码个数</param> /// <returns></returns> private string CreateRandomCode(int length) { int rand; char code; string randomcode = String.Empty; //生成一定长度的验证码 System.Random random = new Random(); for (int i = 0; i < length; i++) { rand = random.Next(); if (rand % 3 == 0) { code = (char)('A' + (char)(rand % 26)); } else { code = (char)('0' + (char)(rand % 10)); } randomcode += code.ToString(); } return randomcode; } /// <summary> /// 创建随机码图片 /// </summary> /// <param name="randomcode">随机码</param> private void CreateImage(string randomcode) { int randAngle = 45; //随机转动角度 int mapwidth = (int)(randomcode.Length * 16); Bitmap map = new Bitmap(mapwidth, 22);//创建图片背景 Graphics graph = Graphics.FromImage(map); graph.Clear(Color.AliceBlue);//清除画面，填充背景 graph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, map.Width - 1, map.Height - 1);//画一个边框 //graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//模式 Random rand = new Random(); //背景噪点生成 Pen blackPen = new Pen(Color.LightGray, 0); for (int i = 0; i < 50; i++) { int x = rand.Next(0, map.Width); int y = rand.Next(0, map.Height); graph.DrawRectangle(blackPen, x, y, 1, 1); } //验证码旋转，防止机器识别 char[] chars = randomcode.ToCharArray();//拆散字符串成单字符数组 //文字距中 StringFormat format = new StringFormat(StringFormatFlags.NoClip); format.Alignment = StringAlignment.Center; format.LineAlignment = StringAlignment.Center; //定义颜色 Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple }; //定义字体 string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" }; int cindex = rand.Next(7); for (int i = 0; i < chars.Length; i++) { int findex = rand.Next(5); Font f = new System.Drawing.Font(font[findex], 14, System.Drawing.FontStyle.Bold);//字体样式(参数2为字体大小) Brush b = new System.Drawing.SolidBrush(c[cindex]); Point dot = new Point(14, 14); //graph.DrawString(dot.X.ToString(),fontstyle,new SolidBrush(Color.Black),10,150);//测试X坐标显示间距的 float angle = rand.Next(-randAngle, randAngle);//转动的度数 graph.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置 graph.RotateTransform(angle); graph.DrawString(chars[i].ToString(), f, b, 1, 1, format); //graph.DrawString(chars[i].ToString(),fontstyle,new SolidBrush(Color.Blue),1,1,format); graph.RotateTransform(-angle);//转回去 graph.TranslateTransform(-2, -dot.Y);//移动光标到指定位置，每个字符紧凑显示，避免被软件识别 } //生成图片 System.IO.MemoryStream ms = new System.IO.MemoryStream(); map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); Response.ClearContent(); Response.ContentType = "image/gif"; Response.BinaryWrite(ms.ToArray()); graph.Dispose(); map.Dispose(); }

用法为新建一个空页面，清除掉页面上的HTML；然后复制一下代码到页面中
用法
protected void Page_Load(object sender, EventArgs e) { string randomcode = CreateRandomCode(4); Session["Code"] = randomcode; //v.CreateValidateGraphic(Page, Session["Code"].ToString()); this.CreateImage(randomcode); }

 

protected void Page_Load(object sender, EventArgs e) { string randomcode = CreateRandomCode(4); Session["Code"] = randomcode; this.CreateImage(randomcode); }

来自：http://www.cnblogs.com/novawu/archive/2010/04/16/1713445.html