学步园

　　 我想大家在申请邮箱或者什么需要注册的地方，就算是大家最熟悉的空间都会出现验证码，那么验证码是什么呢？大家来这里就对咯……

其实验证码呢，就是一个完整的网页，这个网页里面只有大家看到的那个验证码的图片；那又是怎么实现的呢？就在这里啦　！　

　　就像画画，最基本的是一张画布，刷子，画笔等等……很简单，来看一看咯……

//注意：源代码端只需要第一行

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace TwoStore.UI.login
{
    public partial class CodeImage : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            DrapingCodes(ValidateCode());
        }
        private string ValidateCode()
        {
            string result = "";
            string[] codes = { "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "a", "b", "c", "d", "e", "f",
                               "g", "h", "i", "j", "k","l", "m", "n", "o", "p","q", "r", "s", "t", "u", "v",
                               "w", "x", "y", "z"};
            //创建随机数
            Random rand = new Random();
            //rand.Next(codes.Length),随机数的长度为数组的长度
            for (int i = 0; i < 4; i++)
            {
                result += codes[rand.Next(codes.Length)];
            }
            //可以把说的值放在Session中,以判断用户输入的是否显示的验证码
            //也可用Cookie
            Session["code"] = result;
            return result;
        }
        //画图需要导入命名空间System.Drawing;System.Drawing.Imaging;System.IO;                       
        private void DrapingCodes(string code)
        {
            //创建画板---Bitmap---此函数重载12次
            //创建画板时直接规定了它的width,height
            Bitmap bmap = new Bitmap(70, 30);
            //创建画家---并把画布给画家
            Graphics grap = Graphics.FromImage(bmap);
            //让画家把画板图上背景颜色
            grap.Clear(Color.White);
            //创建刷子
            Brush brush = new SolidBrush(Color.Black);
            //创建字体
            Font f = new Font("Comic Sans MS", 15);

            //开始绘画
            grap.DrawString(code, f, brush, 10, 2);

            //随机数
            Random rand = new Random();
            //打上噪点
            for (int i = 0; i < 50; i++)
            {
                bmap.SetPixel(rand.Next(70), rand.Next(30), Color.Black);
            }
            //画笔刷子
            Brush b1 = new SolidBrush(Color.Blue);
            //画笔
            Pen p = new Pen(b1);
            //7,画上几条线
            for (int i = 0; i < 3; i++)
            {
                grap.DrawLine(p, rand.Next(70), rand.Next(30), rand.Next(70), rand.Next(30));
            }
            //定义一个内存流
            MemoryStream ms = new MemoryStream();
            //把图片放到内存流中
            bmap.Save(ms, ImageFormat.Gif);
            //清空输出流
            Response.Clear();
            //设置输出内容的格式
            Response.ContentType = "image/gif";
            //以二进制输出byte[]
            Response.BinaryWrite(ms.ToArray());
            Response.End();
        }
    }
}