生成图片验证码类

using System;
using System.IO;
using System.Web;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;
/// <summary>
///Cls_PicVcode生成图片
/// </summary>
public class ValidateCode
{
    /// <summary>
    /// 该方法用于生成指定位数的随机数
    /// </summary>
    /// <param name="VcodeNum">参数是随机数的位数</param>
    /// <returns>返回一个随机数字符串</returns>
    private string RndNum(int VcodeNum)
    {
        string Vchar = "1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P" +
            ",Q,R,S,T,U,V,W,X,Y,Z";
        string[] VcArray = Vchar.Split(new Char[] { '','' });//拆分成数组
        string VNum = "";//产生的随机数
        int temp = -1;//记录上次随机数值，尽量避免生产几个一样的随机数
        Random rand = new Random();
        for (int i = 1; i < VcodeNum + 1; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
            }
            int t = rand.Next(33);
            if (temp != -1 && temp == t)
            {
                return RndNum(VcodeNum);
            }
            temp = t;
            VNum += VcArray[t];
        }
        return VNum;
    }
    /// <summary>
    /// 该方法是将生成的随机数写入图像文件
    /// </summary>
    /// <param name="VNum">VNum是一个随机数</param>
    public MemoryStream Create(out string VNum)
    {
        VNum = RndNum(4);
        Bitmap Img = null;
        Graphics g = null;
        MemoryStream ms = null;
        System.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(100, 25);

        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 = 0; i < 100; i++)
        {
            int x = random.Next(Img.Width);
            int y = random.Next(Img.Height);
            g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
        }
        //验证码绘制在g中
        for (int i = 0; i < VNum.Length; i++)
        {
            int cindex = random.Next(7);//随机颜色索引值
            int findex = random.Next(5);//随机字体索引值
            Font f = new System.Drawing.Font(fonts[findex], 14, System.Drawing.FontStyle.Bold);//字体
            Brush b = new System.Drawing.SolidBrush(c[cindex]);//颜色
            int ii = 4;
            if ((i + 1) % 2 == 0)//控制验证码不在同一高度
            {
                ii = 2;
            }
            g.DrawString(VNum.Substring(i, 1), f, b, 3 + (i * 20), 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jpg图像文件的格式保存到流中

        //回收资源
        g.Dispose();
        Img.Dispose();
        return ms;

    }
}