using System;        using System.Collections.Generic;        using System.Web;        using System.Web.UI;        using System.Web.UI.WebControls;        using System.Drawing;        using System.IO;        using System.Drawing.Imaging;                public partial class ValidateCode : System.Web.UI.Page        {            private int letterWidth = 16;//单个字体的宽度范围            private int letterHeight = 22;//单个字体的高度范围            private int letterCount = 4;//验证码位数            private char[] chars = "0123456789".ToCharArray();            private string[] fonts = { "Arial", "Georgia" };            /// <summary>            /// 产生波形滤镜效果            /// </summary>            private const double PI = 3.1415926535897932384626433832795;            private const double PI2 = 6.283185307179586476925286766559;            protected void Page_Load(object sender, EventArgs e)            {                //防止网页后退--禁止缓存                    Response.Expires = 0;                Response.Buffer = true;                Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);                Response.AddHeader("pragma", "no-cache");                Response.CacheControl = "no-cache";                string str_ValidateCode = GetRandomNumberString(letterCount);                HttpCookie objCookie = new HttpCookie("ValidateCode");                objCookie.Value = str_ValidateCode;                objCookie.Path = "/";                objCookie.Expires = DateTime.Now.AddSeconds(1200);                Response.Cookies.Add(objCookie);                CreateImage(str_ValidateCode);                    }            public void CreateImage(string checkCode)            {                int int_ImageWidth = checkCode.Length * letterWidth;                Random newRandom = new Random();                Bitmap image = new Bitmap(int_ImageWidth, letterHeight);                Graphics g = Graphics.FromImage(image);                //生成随机生成器                Random random = new Random();                //白色背景                g.Clear(Color.White);                //画图片的背景噪音线                for (int i = 0; i < 10; i++)                {                    int x1 = random.Next(image.Width);                    int x2 = random.Next(image.Width);                    int y1 = random.Next(image.Height);                    int y2 = random.Next(image.Height);                            g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);                }                        //画图片的前景噪音点                for (int i = 0; i < 10; i++)                {                    int x = random.Next(image.Width);                    int y = random.Next(image.Height);                            image.SetPixel(x, y, Color.FromArgb(random.Next()));                }                //随机字体和颜色的验证码字符                        int findex;                for (int int_index = 0; int_index < checkCode.Length; int_index++)                {                    findex = newRandom.Next(fonts.Length - 1);                    string str_char = checkCode.Substring(int_index, 1);                    Brush newBrush = new SolidBrush(GetRandomColor());                    Point thePos = new Point(int_index * letterWidth + 1 + newRandom.Next(3), 1 + newRandom.Next(3));//5+1+a+s+p+x                    g.DrawString(str_char, new Font(fonts[findex], 12, FontStyle.Bold), newBrush, thePos);                }                //灰色边框                g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth - 1, (letterHeight - 1));                //图片扭曲                //image = TwistImage(image, true, 3, 4);                //将生成的图片发回客户端                MemoryStream ms = new MemoryStream();                image.Save(ms, ImageFormat.Png);                Response.ClearContent(); //需要输出图象信息 要修改HTTP头                 Response.ContentType = "image/Png";                Response.BinaryWrite(ms.ToArray());                g.Dispose();                image.Dispose();            }            /// <summary>            /// 正弦曲线Wave扭曲图片            /// </summary>            /// <param name="srcBmp">图片路径</param>            /// <param name="bXDir">如果扭曲则选择为True</param>            /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高，一般为3</param>            /// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param>            /// <returns></returns>            public System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)            {                System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);                // 将位图背景填充为白色                System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);                graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);                graph.Dispose();                double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;                        for (int i = 0; i < destBmp.Width; i++)                {                    for (int j = 0; j < destBmp.Height; j++)                    {                        double dx = 0;                        dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;                        dx += dPhase;                        double dy = Math.Sin(dx);                        // 取得当前点的颜色                        int nOldX = 0, nOldY = 0;                        nOldX = bXDir ? i + (int)(dy * dMultValue) : i;                        nOldY = bXDir ? j : j + (int)(dy * dMultValue);                        System.Drawing.Color color = srcBmp.GetPixel(i, j);                        if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height)                        {                            destBmp.SetPixel(nOldX, nOldY, color);                        }                    }                }                return destBmp;            }                    public Color GetRandomColor()            {                Random RandomNum_First = new Random((int)DateTime.Now.Ticks);                System.Threading.Thread.Sleep(RandomNum_First.Next(50));                Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);                int int_Red = RandomNum_First.Next(210);                int int_Green = RandomNum_Sencond.Next(180);                int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green;                int_Blue = (int_Blue > 255) ? 255 : int_Blue;                return Color.FromArgb(int_Red, int_Green, int_Blue);// 5+1+a+s+p+x            }                    //  生成随机数字字符串            public string GetRandomNumberString(int int_NumberLength)            {                Random random = new Random();                string validateCode = string.Empty;                for (int i = 0; i < int_NumberLength; i++)                    validateCode += chars[random.Next(0, chars.Length)].ToString();                return validateCode;            }        }  

    <img alt="看不清，换一张" title="看不清，换一张" src="ValidateCode.aspx" style="cursor:pointer" onclick="this.src=this.src+'?r='+Math.random()" />