using System;

using System.Collections.Generic;

using System.IO;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

namespace ValidateCodeDemo

{

    public class ValidateCodeHelper

    {

        /// <summary>

        /// 生成验证码

        /// </summary>

        /// <param name="length">指定验证码的长度</param>

        /// <returns></returns>

        public static string CreateValidateCode(int length)

        {

            int[] randMembers = new int[length];

            int[] validateNums = new int[length];

            string validateNumberStr = "";

            //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 += validateNums[i].ToString();

            }

            return validateNumberStr;

        }

        /// <summary>

        /// 创建验证码的图片

        /// </summary>

        /// <param name="validateCode">验证码</param>

        public static byte[] CreateValidateGraphic(string validateCode)

        {

            Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), );

            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);

                //画图片的干扰线

                for (int i = ; i < ; 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 Font("Arial", , (FontStyle.Bold | FontStyle.Italic));

                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(, , image.Width, image.Height),

                 Color.Blue, Color.DarkRed, 1.2f, true);

                g.DrawString(validateCode, font, brush, , );

                //画图片的前景干扰点

                for (int i = ; i < ; 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), , , image.Width - , image.Height - );

                //保存图片数据

                MemoryStream stream = new MemoryStream();

                image.Save(stream, ImageFormat.Jpeg);

                //输出图片流

                return stream.ToArray();

            }

            finally

            {

                g.Dispose();

                image.Dispose();

            }

        }

    }

}