【验证码生成】asp.net验证码图片生成示例-验证码图片生成

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asp.net验证码图片生成示例

public partial class ValidateImage : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            this.CreateCheckCodeImage(RndNum());
        }

        /// <summary>生成验证码
        /// </summary>
        /// <returns></returns>
        private string RndNum()
        {
            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
                    code=(char)('A' + (char)(number % 26));
                checkCode +=code.ToString();
            }
            Response.Cookies.Add(new HttpCookie("yzmcode", checkCode));
            return checkCode;
        }

        /// <summary>向页面生成验证码Gif图片
        /// </summary>
        /// <param name="checkCode"></param>
        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 * 12.5)), 22);
            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.White);
                //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.Silver), x1, y1, x2, y2);
                }

                Font font=new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | 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);
                g.DrawString(checkCode, font, brush, 2, 2);
                //画图片的前景噪音点
                for (int i=0; i < 100; 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();
            }
        }

    }

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