ASP.NET 简单清晰的一个验证码

//页面 调用
<div style="float:left; padding-top:1px; padding-left:5px;">
<img src="validitycode.aspx" alt="看不清，换一张" onclick="var r=Math.random();
this.src='/validitycode.aspx?r='+r" style="cursor:pointer;" /></div>

 

 

//添加一个validitycode.aspx 后台代码

public partial class validitycode : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Response.AddHeader("Expires", "0");
            Response.AddHeader("Cache-Control", "no-cache");
            Response.AddHeader("Cache-Control", "must-revalidate");

            //base.Page_Load(sender, e);
            this.CreateCheckCodeImage(GenerateCheckCode());
        }

        protected string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;

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

                    if (number % 2 == 0)
                        code = (char)('1' + (char)(number % 9));
                    else
                        code = (char)('A' + (char)(number % 26));

                } while (checkCode.Contains(code.ToString()));

                checkCode += code.ToString();
            }

            SessionManager.Identitycode = checkCode;

            return checkCode;
        }

        private void CreateCheckCodeImage(string checkCode)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
                return;

            System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 15.0)), 25);
            Graphics g = Graphics.FromImage(image);

            try
            {
                //生成随机生成器
                Random random = new Random();

                //清空图片背景色
                g.Clear(Color.FromArgb(166, 255, 186));

                ////画图片的背景噪音线
                //for (int i = 0; i < 25; 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.DarkGray), x1, y1, x2, y2);
                //}

                Color forecolor1 = Color.FromArgb(255, 0, 0);
                Color forecolor2 = Color.FromArgb(0, 0, 255);

                Font font = new System.Drawing.Font("Arial", 14F, (System.Drawing.FontStyle.Regular | System.Drawing.FontStyle.Italic));
                //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);
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), forecolor1, forecolor2, 1.2f, true);
                g.DrawString(checkCode, font, brush, 0, 1);

                //Random random1 = new Random();
                //image = TwistImage(image, true, (double)random1.Next(-30, 30) / 10, (double)random1.Next(-30, 30) / 10);//random1.Next(10, 23), random1.Next(1, 8));//22.33, 0.03);

                ////画图片的前景噪音点
                //for (int i = 0; i < 50; i++)
                //{
                //    int x = random.Next(image.Width);
                //    int y = random.Next(image.Height);

                //    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                //}

                //画图片的边框线
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                Response.ClearContent();
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }

        /// <summary>
        /// 正弦曲线Wave扭曲图片
        /// </summary>
        /// <param name="srcBmp"></param>
        /// <param name="bXDir"></param>
        /// <param name="nMultValue">波形的幅度倍数</param>
        /// <param name="dPhase">波形的起始相位，取值区间[0-2*PI)</param>
        /// <returns></returns>
        private Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
        {
            double PI = 6.283185307179586476925286766559;
            Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);

            // 将位图背景填充为白色
            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 ? (PI * (double)j) / dBaseAxisLen : (PI * (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);

                    Color color = srcBmp.GetPixel(i, j);
                    if (nOldX >= 0 && nOldX < destBmp.Width
                     && nOldY >= 0 && nOldY < destBmp.Height)
                    {
                        destBmp.SetPixel(nOldX, nOldY, color);
                    }
                }
            }
            srcBmp.Dispose();
            return destBmp;
        }

    }