验证码类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Drawing;
using System.Web.SessionState;

namespace RPSite.Ctrls.Captcha
{
    /// <summary>
    /// $codebehindclassname$ 的摘要说明
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    public class Captcha : IHttpHandler, IRequiresSessionState
    {

        public void ProcessRequest(HttpContext context)
        {
            var Response = context.Response;
            Response.ContentType = "image/jpeg"; //需要输出图象信息 要修改HTTP头 

            int size = 5;//验证码的长度

            string authCode = GetRandomNumberString(size);// 获得验证码字符

            //在生成验证码的地方将验证码放到Session中，这样在用的时候就能从Session中取出正确的验证码了
            context.Session["AuthCode"] = authCode;
            using (Bitmap theBitmap = CreateImage(authCode))// 获得验证码图片
            {
                theBitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            Response.End();
        }

        /// <summary>
        /// 返回验证码字符
        /// </summary>
        /// <param name="codeCount">验证码长度</param>
        /// <returns></returns>
        private string GetRandomNumberString(int codeCount)
        {
            string strChoice = "2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";
            string[] strResult = strChoice.Split(new Char[] { ',' });
            string strReturn = "";
            Random rnd = new Random();
            for (int i = 0; i < codeCount; i++)
            {
                int j = rnd.Next(strResult.Length);//随机数不能大于数组的长度
                strReturn = strReturn + strResult[j].ToString();
            }
            return strReturn;
        }

        private Bitmap CreateImage(string str_AuthCode)
        {
            int width = str_AuthCode.Length * 13;
            int height = 20;
            Random rad = new Random();
            Bitmap bmp = new Bitmap(width, height);
            using (Graphics grp = Graphics.FromImage(bmp))
            {
                grp.Clear(Color.White);//填充bmp的背景色
                grp.DrawRectangle(new Pen(Color.Red, 1), 0, 0, width - 1, height - 1);//绘制边框
                int num = width * height;
                for (int i = 0; i < num; i += 3)//在图片的指定坐标上画上有颜色的圆点
                {
                    int x = rad.Next(width);
                    int y = rad.Next(height);
                    int r = rad.Next(255);
                    int g = rad.Next(255);
                    int b = rad.Next(255);
                    Color c = Color.FromArgb(r, g, b);
                    bmp.SetPixel(x, y, c);//在图片的指定坐标上画上有颜色的圆点
                }

                using (Font f = new Font("宋体", 12, FontStyle.Bold))//定义字体
                {
                    using (Brush br = new SolidBrush(Color.Black))//定义画笔的颜色及字体的颜色
                    {
                        for (int i = 0; i < str_AuthCode.Length; i++)
                        {
                            string s = str_AuthCode.Substring(i, 1);//单个单个的将字画到图片上
                            Point p = new Point(i * 12 + rad.Next(3), rad.Next(3) + 1);//字体出现的位置（坐标）
                            grp.DrawString(s, f, br, p);//绘制字符串
                        }
                    }
                }
                return bmp;//返回
            }
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}