using System;

using System.IO;

using System.DrawingCore;

using System.DrawingCore.Imaging;

namespace MobileWeb.Utility

{

    public class Captcha

    {

        public string CreateValidateNumber(int length)

        {

            int[] randMembers = new int[length];

            int[] validateNums = new int[length];

            System.Text.StringBuilder validateNumberStr = new System.Text.StringBuilder();

            //生成起始序列值

            int seekSeek = unchecked((int)DateTime.Now.Ticks);

            Random seekRand = new Random(seekSeek);

            int beginSeek = (int)seekRand.Next(, Int32.MaxValue - length * );

            int[] seeks = new int[length];

            for (int i = ; i < length; i++)

            {

                beginSeek += ;

                seeks[i] = beginSeek;

            }

            //生成随机数字

            for (int i = ; i < length; i++)

            {

                Random rand = new Random(seeks[i]);

                int pownum =  * (int)Math.Pow(, length);

                randMembers[i] = rand.Next(pownum, Int32.MaxValue);

            }

            //抽取随机数字

            for (int i = ; i < length; i++)

            {

                string numStr = randMembers[i].ToString();

                int numLength = numStr.Length;

                Random rand = new Random();

                int numPosition = rand.Next(, numLength - );

                validateNums[i] = Int32.Parse(numStr.Substring(numPosition, ));

            }

            //生成验证码

            for (int i = ; i < length; i++)

            {

                validateNumberStr.Append(validateNums[i].ToString());

            }

            return validateNumberStr.ToString();

        }

        public byte[] CreateValidateGraphic(string validateNum)

        {

            Bitmap Img = null;

            Graphics g = null;

            MemoryStream ms = null;

            Random random = new Random();

            //验证码颜色集合

            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };

            //验证码字体集合

            string[] fonts = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };

            //定义图像的大小，生成图像的实例

            Img = new Bitmap((int)validateNum.Length * , );

            g = Graphics.FromImage(Img);//从Img对象生成新的Graphics对象    

            g.Clear(Color.White);//背景设为白色  

            //在随机位置画背景点

            for (int i = ; i < ; i++)

            {

                int x = random.Next(Img.Width);

                int y = random.Next(Img.Height);

                g.DrawRectangle(new Pen(Color.LightGray, ), x, y, , );

            }

            //验证码绘制在g中

            for (int i = ; i < validateNum.Length; i++)

            {

                int cindex = random.Next();//随机颜色索引值

                int findex = random.Next();//随机字体索引值

                Font f = new Font(fonts[findex], , FontStyle.Bold);//字体

                Brush b = new SolidBrush(c[cindex]);//颜色

                int ii = ;

                if ((i + ) %  == )//控制验证码不在同一高度

                {

                    ii = ;

                }

                g.DrawString(validateNum.Substring(i, ), f, b,  + (i * ), ii);//绘制一个验证字符

            }

            ms = new MemoryStream();//生成内存流对象

            Img.Save(ms, ImageFormat.Jpeg);//将此图像以Png图像文件的格式保存到流中  

            //回收资源

            g.Dispose();

            Img.Dispose();

            return ms.ToArray();

        }

    }

}

        public ActionResult ValidateCode()

        {

            Captcha captcha = new Captcha();

            var code = captcha.CreateValidateNumber();

            HttpContext.Session.SetString("ValidateCode", code);

            return File(captcha.CreateValidateGraphic(code), "image/jpeg");

        }