<%@ WebHandler Language="C#" Class="WaterMark" %>

using System;
using System.Web;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Web.SessionState;  

public class WaterMark : IHttpHandler, IRequiresSessionState  // 要使用session必須實(shí)現(xiàn)該接口,記得要導(dǎo)入System.Web.SessionState命名空間
{

    public void ProcessRequest(HttpContext context)
    {
        string checkCode = GenCode(5);  // 產(chǎn)生5位隨機(jī)字符
        context.Session["Code"] = checkCode; //將字符串保存到Session中，以便需要時(shí)進(jìn)行驗(yàn)證
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 22);
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成隨機(jī)生成器
            Random random = new Random();

            //清空?qǐng)D片背景色
            g.Clear(Color.White);

            // 畫(huà)圖片的背景噪音線
            int i;
            for (i = 0; i < 25; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Height);
                int y2 = random.Next(image.Height);
                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
            }

            Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2F, true);
            g.DrawString(checkCode, font, brush, 2, 2);

            //畫(huà)圖片的前景噪音點(diǎn)
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            context.Response.ClearContent();
            context.Response.ContentType = "image/Gif";
            context.Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }

    /// <summary>
    /// 產(chǎn)生隨機(jī)字符串
    /// </summary>
    /// <param name="num">隨機(jī)出幾個(gè)字符</param>
    /// <returns>隨機(jī)出的字符串</returns>
    private string GenCode(int num)
    {
        string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//"的一是在不了有和人這中大為上個(gè)國(guó)我以要他時(shí)來(lái)用們生到作地于出就分對(duì)成會(huì)可主發(fā)年動(dòng)同工也能下過(guò)子說(shuō)產(chǎn)種面而方后多定行學(xué)法所民得經(jīng)十三之進(jìn)著等部度家電力里如水化高自二理起小物現(xiàn)實(shí)加量都兩體制機(jī)當(dāng)使點(diǎn)從業(yè)本去把性好應(yīng)開(kāi)它合還因由其些然前外天政四日那社義事平形相全表間樣與關(guān)各重新線內(nèi)數(shù)正心反你明看原又么利比或但質(zhì)氣第向道命此變條只沒(méi)結(jié)解問(wèn)意建月公無(wú)系軍很情者最立代想已通并提直題黨程展五果料象員革位入常文總次品式活設(shè)及管特件長(zhǎng)求老頭基資邊流路級(jí)少圖山統(tǒng)接知較將組見(jiàn)計(jì)別她手角期根論運(yùn)農(nóng)指幾九區(qū)強(qiáng)放決西被干做必戰(zhàn)先回則任取據(jù)處隊(duì)南給色光門即保治北造百規(guī)熱領(lǐng)七海口東導(dǎo)器壓志世金增爭(zhēng)濟(jì)階油思術(shù)極交受聯(lián)什認(rèn)六共權(quán)收證改清己美再采轉(zhuǎn)更單風(fēng)切打白教速花帶安場(chǎng)身車?yán)鎰?wù)具萬(wàn)每目至達(dá)走積示議聲報(bào)斗完類八離華名確才科張信馬節(jié)話米整空元況今集溫傳土許步群廣石記需段研界拉林律叫且究觀越織裝影算低持音眾書(shū)布復(fù)容兒須際商非驗(yàn)連斷深難近礦千周委素技備半辦青省列習(xí)響約支般史感勞便團(tuán)往酸歷市克何除消構(gòu)府稱太準(zhǔn)精值號(hào)率族維劃選標(biāo)寫(xiě)存候毛親快效斯院查江型眼王按格養(yǎng)易置派層片始卻專狀育廠京識(shí)適屬圓包火住調(diào)滿縣局照參紅細(xì)引聽(tīng)該鐵價(jià)嚴(yán)";
        char[] chastr = str.ToCharArray();
        // string[] source ={ "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "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", "#", "$", "%", "&", "@" };
        string code = "";
        Random rd = new Random();
        int i;
        for (i = 0; i < num; i++)
        {
            //code += source[rd.Next(0, source.Length)];
            code += str.Substring(rd.Next(0, str.Length), 1);
        }
        return code;

    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}