生成图片验证码方法

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>
namespace 生成图片验证码方法
{
    public class ImageValidate
    {
        /// <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>
        public static 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 static MemoryStream Create(string VNum)
        {
            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" };

            Img = new Bitmap(90, 25);     //定义图像的大小，生成图像的实例
            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
           
            for (int i = 0; i < 90; i++)  //在随机位置画背景点
            {
                int x = random.Next(Img.Width);
                int y = random.Next(Img.Height);
                g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
            }
       
            for (int i = 0; i < VNum.Length; i++)    //验证码绘制在g中
            {
                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 Font(fonts[findex], 12, System.Drawing.FontStyle.Bold); //设置字体风格
                Brush b = new System.Drawing.SolidBrush(c[cindex]); //设置字体的颜色
                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
        
            g.Dispose();   //回收资源
            Img.Dispose();
            return ms;
        }
    }
}