asp.net图片验证码实例

下面代码文件名是ValidateCode.ashx

    public class ValidateCode :  IHttpHandler, IRequiresSessionState
    {
        /// <summary>
        /// 验证码|使用事例:<img src="../tools/ValidateCode.ashx" onclick="this.src='../tools/ValidateCode.ashx'"alt="看不清验证码,请单击" style="cursor: hand; width: 52px; height: 18px;" />
        /// </summary>
        /// <param name="context"></param>
        public void ProcessRequest(HttpContext context)
        {
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            context.Response.ContentType = "text/plain";
            int w = Common.CFun.GetQueryInt("w", HttpContext.Current);
            w = w > 0 ? w : 63;
            int h = Common.CFun.GetQueryInt("h", HttpContext.Current);
            h = h > 0 ? h : 30;

            string checkCode = GenerateCheckCode();
            context.Session["CheckCode"] = checkCode;//将验证码写入Session
            Bitmap image = CreateCheckCodeImage(checkCode, w, h);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            context.Response.ClearContent();
            context.Response.ContentType = "image/Gif";
            context.Response.BinaryWrite(ms.ToArray());
        }

        /// <summary>
        /// 得到验证码
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        private string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;

            System.Random random = new Random();

            for (int i = 0; i < 4; i++)
            {
                number = random.Next();

                if (number % 2 == 0)
                    code = (char)('0' + (char)(number % 10));
                else if (number % 3 == 0)
                    code = (char)('A' + (char)(number % 26));
                else
                    code = (char)('a' + (char)(number % 26));
                checkCode += code.ToString();
            }
            return checkCode.ToUpper();
        }

        /// <summary>
        /// 生成验证码图片
        /// </summary>
        /// <param name="checkCode"></param>
        /// <param name="context"></param>
        private Bitmap CreateCheckCodeImage(string checkCode, int w = 54, int h = 30)
        {
            System.Drawing.Bitmap image = new System.Drawing.Bitmap(w, h);
            Graphics g = Graphics.FromImage(image);

            g.Clear(Color.WhiteSmoke);//清除背景色

            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };//定义随机颜色

            string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
            Random rand = new Random();
            int z = 0;//干扰线条数
            for (int i = 0; i < z; i++)
            {
                int x1 = rand.Next(image.Width);
                int x2 = rand.Next(image.Width);
                int y1 = rand.Next(image.Height);
                int y2 = rand.Next(image.Height);
                g.DrawLine(new Pen(Color.LightGray, 1), x1, y1, x2, y2);//根据坐标画线
            }

            for (int i = 0; i < checkCode.Length; i++)
            {
                int cindex = rand.Next(7);
                int findex = rand.Next(5);

                Font f = new System.Drawing.Font(font[findex], 14, System.Drawing.FontStyle.Bold);
                Brush b = new System.Drawing.SolidBrush(c[cindex]);
                int ii = 4;
                if ((i + 1) % 2 == 0)
                {
                    ii = 2;
                }
                g.DrawString(checkCode.Substring(i, 1), f, b, 3 + (i * (14)), ii);
            }
            image = TwistImage(image, true, 5, 1);
            g.DrawRectangle(new Pen(Color.Black, 0), 0, 0, image.Width - 1, image.Height - 1);
            return image;
        }
        #region 产生波形滤镜效果

        private const double PI = 3.1415926535897932384626433832795;
        private const double PI2 = 6.283185307179586476925286766559;

        /// <summary>
        /// 正弦曲线Wave扭曲图片(Edit By 51aspx.com)
        /// </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;
        }



        #endregion
        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }


以下调用方法

 
 <span class="ckcinput">
 <img id="checkCodeImg" src="/ValidateCode.ashx" align="absmiddle" onclick="changeCC()"alt="看不清验证码,请单击" style="cursor: pointer; width: 56px; height: 30px; margin-top: 5px;margin-left: 2px;" />
</span>

JS代码方法

function changeCC() {
            $("#checkCodeImg").attr("src", "/ValidateCode.ashx?" + Math.random());
        }


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