验证码生成

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Drawing.Imaging;

namespace Common
{
    public class ValidateCode
    {
        //验证码长度
        private int codeLength;

        //初始化验证码长度
        public ValidateCode(int codeLength)
        {
            this.codeLength = codeLength;
        }

        //生成验证码字符串 数字+字符串
        public string CreateValidateCode()
        {
            int[] randCode = new int[codeLength];
            int[] randNum = new int[codeLength];
            string validateStr = "";

            //获取  得到随机数的随机率有关的数字
            int seek = (int)DateTime.Now.Ticks;//可能会有问题，因为DateTime.Now.Ticks可能超过int类型

            Random rand = new Random(seek);
            //获取一个随机数作为随机数的开始
            int beginRand = rand.Next(0, int.MaxValue - codeLength * 10000);
            int[] seeks = new int[codeLength];
            for (int i = 0; i < codeLength; i++)
            {
                beginRand += 10000;
                seeks[i] = beginRand;
            }
            //给每个生成的随机数给不同的随机率
            for (int j = 0; j < codeLength; j++)
            {
                Random r = new Random(seeks[j]);
                int powNum = (int)Math.Pow(10, codeLength);
                randNum[j] = r.Next(powNum, int.MaxValue);
            }
            //randNum 保存了四个随机数
            for (int k = 0; k < codeLength; k++)
            {
                string numStr = randNum[k].ToString();
                int numLen = numStr.Length;
                Random r = new Random();
                int numPostion = r.Next(0, numLen - 1);
                randCode[k] = int.Parse(numStr.Substring(numPostion, 1));
            }
            for (int i = 0; i < codeLength; i++)
            {
                validateStr += randCode[i].ToString();
            }
            return validateStr;
        }


        public byte[] CreateVCodeImg(string validateCode)
        {
            //初始化一张图像，点位图 图像的大小：长Math.Ceiling（validateCode.Length * 12.0） 宽：24 px
                Bitmap bitmap = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 24);
                //准备一张画笔  专门为某个图像准备的画笔
                Graphics g = Graphics.FromImage(bitmap);//Graphics和Bitmap继承了IDisposable接口 所以最好使用后释放
                try
                {


                    Random random = new Random();

                    //用画笔把图像的背景色清空（填充成白色的图像背景）
                    g.Clear(Color.White);

                    //画干扰线 循环25次 每次4个数 生成两个点 25条（有可能线被覆盖）
                    //每次循环生成一条线
                    for (int i = 0; i < 25; i++)
                    {
                        int linex1 = random.Next(bitmap.Width);
                        int linex2 = random.Next(bitmap.Width);
                        int liney1 = random.Next(bitmap.Height);
                        int liney2 = random.Next(bitmap.Height);
                        g.DrawLine(new Pen(Color.Silver), linex1, liney1, linex2, liney2);
                    }
                    //准备
                    Font f = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
                    LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, bitmap.Width, bitmap.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                    //把验证码字符串用画笔画到bitmap上
                    g.DrawString(validateCode, f, brush, 3, 2);
                    //生成像素点 验证码图片中的干扰点 会覆盖在文字 画的先后顺序
                    for (int j = 0; j < 100; j++)
                    {
                        int x = random.Next(bitmap.Width);
                        int y = random.Next(bitmap.Height);
                        bitmap.SetPixel(x, y, Color.FromArgb(random.Next()));
                    }
                    //画图片的边框线 边框线在图片的里面 所以边框线不能和bitmap同样大小
                    g.DrawRectangle(new Pen(Color.Silver), 0, 0, bitmap.Width - 1, bitmap.Height - 1);
                    //保存图片 把图片输出要把图片转化成流输出 内存流
                    MemoryStream ms = new MemoryStream();
                    bitmap.Save(ms, ImageFormat.Jpeg);
                    //输出图片流
                    return ms.ToArray();
                }
                finally
                {
                    g.Dispose();
                    bitmap.Dispose();
                }
        }
    }
}