c#验证码问题

新加一个asp页面（CreateImage.aspx），前端什么也没有，后端只需要如下代码。

用的时候是需要将image的src指向该页面即可；祝后台生成的验证码通过session传递过来,如红色标注部分

 

   public partial class CreateImage : System.Web.UI.Page
    {
        #region 设置验证码
        // 验证码长度
        private int codeLen = 4;
        // 图片清晰度
        private int fineness = 95;
        // 图片宽度
        private int imgWidth = 80;
        // 图片高度
        private int imgHeight = 37;
        // 字体家族名称
        private string fontFamily = "Arial";
        // 字体大小
        private int fontSize = 15;
        // 字体样式
        private int fontStyle = 3;
        // 绘制起始坐标 X
        private int posX = 16;
        // 绘制起始坐标 Y
        private int posY = 7;

        private static char[] allCharArray = new char[] { '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };

        #endregion

        private void Page_Load(object sender, System.EventArgs e)
        {
            #region 读取 Request 传递参数
            // 获取代码长度设置
            if (Request["CodeLen"] != null)
            {
                try
                {
                    codeLen = Int32.Parse(Request["CodeLen"]);

                    // 规定验证码长度
                    if (codeLen < 4 || codeLen > 16)
                        throw new Exception("验证码长度必须在4到16之间");
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }

            // 获取图片清晰度设置
            if (Request["Fineness"] != null)
            {
                try
                {
                    fineness = Int32.Parse(Request["Fineness"]);

                    // 验证清晰度
                    if (fineness < 0 || fineness > 100)
                        throw new Exception("图片清晰度必须在0到100之间");
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }

            // 获取图片宽度
            if (Request["ImgWidth"] != null)
            {
                try
                {
                    imgWidth = Int32.Parse(Request["ImgWidth"]);

                    if (imgWidth < 16 || imgWidth > 480)
                        throw new Exception("图片宽度必须在16到480之间");
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }

            // 获取图片高度
            if (Request["ImgHeight"] != null)
            {
                try
                {
                    imgWidth = Int32.Parse(Request["ImgHeight"]);

                    if (imgWidth < 16 || imgWidth > 320)
                        throw new Exception("图片高度必须在16到320之间");
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }

            // 获取验证码字体家族名称
            if (Request["FontFamily"] != null)
            {
                fontFamily = Request["FontFamily"];
            }

            // 获取验证码字体大小
            if (Request["FontSize"] != null)
            {
                try
                {
                    fontSize = Int32.Parse(Request["FontSize"]);

                    if (fontSize < 8 || fontSize > 72)
                        throw new Exception("字体大小必须在8到72之间");
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }

            // 获取字体样式
            if (Request["FontStyle"] != null)
            {
                try
                {
                    fontStyle = Int32.Parse(Request["FontStyle"]);
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }

            // 验证码绘制起始位置 X
            if (Request["PosX"] != null)
            {
                try
                {
                    posX = Int32.Parse(Request["PosX"]);
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }

            // 验证码绘制起始位置 Y
            if (Request["PosY"] != null)
            {
                try
                {
                    posY = Int32.Parse(Request["PosY"]);
                }
                catch (Exception Ex)
                {
                    throw Ex;
                }
            }
            #endregion

            string validateCode = CreateValidateCode();

            // 生成BITMAP图像
            Bitmap bitmap = new Bitmap(imgWidth, imgHeight);

            // 给图像设置干扰
            DisturbBitmap(bitmap);

            // 绘制验证码图像
            DrawValidateCode(bitmap, validateCode);

            bitmap = TwistImage(bitmap,true,4,2);

 

            // 保存验证码图像，等待输出
            bitmap.Save(Response.OutputStream, ImageFormat.Gif);

            bitmap.Dispose();
        }

        /// <summary>
        /// 随机生成验证码,并把验证码保存到Session中.
        /// </summary>
        /// <returns></returns>
        private string CreateValidateCode()
        {

            #region 0-9数字的验证码

            string randomCode = "";
            int t = 0;

            Random rand = new Random();
            for (int i = 0; i < codeLen; i++)
            {
                t = rand.Next(allCharArray.Length);

                randomCode += allCharArray[t];
            }

            Session["CheckCode"] = randomCode;
            return randomCode;

            #endregion
        }

        /// <summary>
        /// 为图片设置干扰点
        /// </summary>
        /// <param name="bitmap"></param>
        private void DisturbBitmap(Bitmap bitmap)
        {
            // 通过随机数生成
            Random random = new Random();

            for (int i = 0; i < bitmap.Width; i++)
            {
                for (int j = 0; j < bitmap.Height; j++)
                {
                    if (random.Next(100) <= this.fineness)
                        bitmap.SetPixel(i, j, Color.White);
                }
            }
        }

        /// <summary>
        /// 绘制验证码图片
        /// </summary>
        /// <param name="bitmap"></param>
        /// <param name="validateCode"></param>
        private void DrawValidateCode(Bitmap bitmap, string validateCode)
        {
            // 获取绘制器对象
            Graphics g = Graphics.FromImage(bitmap);

            // 设置绘制字体
            Font font = new Font(fontFamily, fontSize, GetFontStyle());

            // 绘制验证码图像
            g.DrawString(validateCode, font, Brushes.Black, posX, posY);

            font.Dispose();
            g.Dispose();
        }

        /// <summary>
        /// 换算验证码字体样式：1 粗体 2 斜体 3 粗斜体，默认为普通字体
        /// </summary>
        /// <returns></returns>
        private FontStyle GetFontStyle()
        {
            if (fontStyle == 1)
                return FontStyle.Bold;
            else if (fontStyle == 2)
                return FontStyle.Italic;
            else if (fontStyle == 3)
                return FontStyle.Bold | FontStyle.Italic;
            else
                return FontStyle.Regular;
        }

        #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
        /// </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 Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
        {
            Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);

            // 将位图背景填充为白色
            System.Drawing.Graphics graph = Graphics.FromImage(destBmp);
            graph.FillRectangle(new SolidBrush(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
   
   
    }