using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Web;  
using System.Drawing;  
using System.IO;  

namespace BookShop.Web  
{  
    public class WaterMark : IHttpHandler  
    {  

        private const string WATERMARK_URL = "~/Images/watermark.jpg";        //水印圖片  
        private const string DEFAULTIMAGE_URL = "~/Images/default.jpg";<span style="white-space:pre">   </span>      //默認圖片  
        #region IHttpHandler 成員  

        public bool IsReusable  
        {  
            get { return false; }  
        }  

        public void ProcessRequest(HttpContext context)  
        {  

            //context.Request.PhysicalPath  //獲得用戶請求的文件物理路徑  

            System.Drawing.Image Cover;  
            //判斷請求的物理路徑中，是否存在文件  
            if (File.Exists(context.Request.PhysicalPath))  
            {  
                //加載文件  
                Cover = Image.FromFile(context.Request.PhysicalPath);  
                //加載水印圖片  
                Image watermark = Image.FromFile(context.Request.MapPath(WATERMARK_URL));  
            //通過書的封面得到繪圖對像  
                Graphics g = Graphics.FromImage(Cover);  
                //在image上繪制水印  
                g.DrawImage(watermark, new Rectangle(Cover.Width - watermark.Width, Cover.Height - watermark.Height,   
[csharp] view plaincopy
watermark.Width, watermark.Height), 0, 0, watermark.Width, watermark.Height, GraphicsUnit.Pixel);  
                //釋放畫布  
                g.Dispose();  
                //釋放水印圖片  
                watermark.Dispose();  
            }  
            else 
            {  
                //加載默認圖片  
                Cover = Image.FromFile(context.Request.MapPath(DEFAULTIMAGE_URL));  
            }  
            //設置輸出格式  
            context.Response.ContentType = "image/jpeg";  
            //將圖片存入輸出流  
            Cover.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);  
            Cover.Dispose();  
            context.Response.End();  
        }  

        #endregion  
    }  
}