圣誕節，25日，要交ACCP5.0認證的項目，其中有這樣一個要求：書店的所有圖書的封面放在了\images\convers\下面，要求所有引用這一路徑下的圖片都添加書店的店名水印圖片。就是說攔截Http請求了，自然想到HttpHandler可以辦到。考慮下，實現的效果應該是這樣的：為了通用，監視的路徑，水印圖片路徑，默認圖片路徑3者應該在配置文件里面設定，方便修改；監視路徑下的所有圖片只要物理存在都要有水印，物理不存在用默認圖片替代，若水印圖片不存在用文字代替。訪問其他路徑下的圖片應該正常顯示沒有水印....廢話不多說，實現的代碼如下：為方便調試，編譯httpHandler類的時候要加調試選項，并在項目中引用這個dll（編譯：csc /t:library WatermarkHandler.cs /debug)
using?System;
using?System.Data;
using?System.Configuration;
using?System.Web;
using?System.Web.Security;
using?System.Web.UI;
using?System.Web.UI.HtmlControls;
using?System.Web.UI.WebControls;
using?System.Web.UI.WebControls.WebParts;

namespace?xumh
{
????/**////?<summary>
????///?圖片處理模塊：給指定路徑下的圖片添加水印輸出
????///?1.監視的目錄路徑，水印圖片路徑，默認圖片三者都在web.config文件中設定
????///?2.請求的圖片的路徑不屬于監視路徑，直接輸出圖片
????///?3.請求的圖片的路徑屬于監視路徑，若圖片不存在，顯示默認圖片，不加水印
????///?4.請求的圖片的路徑屬于監視路徑，且文件存在，添加水印
????///????????水印圖片存在：圖片+水印圖片，輸出
????///????????水印圖片不存在：圖片+水印文字，輸出
????///????????
????///?5.web.config部分如下：
????///?????????<appSettings>
????///??????????????????<!--要監視的路徑-->
????///?????????????????????<add?key="monitorPath"?value="/images/bookcovers/"/>
????///?????????????????<!--圖書封面不存在時顯示的默認封面圖片的相對路徑-->
????///????????????????????<add?key="defaultImage"?value="images\default.jpg"/>
????///?????????????????<!--相對于物理應用程序的根路徑的水印圖片的相對路徑-->
????///??????????????????????<add?key="watermarkImage"?value="images\WaterMark.jpg"/>
????///????????</appSettings>
????///?????
????///?????????<httpHandlers>
????///????????????????<add?verb="*"?path="*.jpg"?type="xumh.WatermarkHandler,WatermarkHandler"/>
????///????????????</httpHandlers>
????///???????許明會??2007-12-23?18:00?Visual?Studio?2005?調試通過
????///?</summary>
????public?class?WatermarkHandler:IHttpHandler
????{
????????public?bool?IsReusable
????????{
????????????get?{?return?true;?}
????????}

????????public?void?ProcessRequest(HttpContext?context)
????????{
????????????string?url?=?context.Request.Url.AbsoluteUri.ToLower();
????????????string?monitorPath?=?System.Configuration.ConfigurationManager.AppSettings["monitorPath"];
????????????//若圖片不屬于封面，直接輸出圖片:若圖片不存在不做處理
????????????bool?IsInterestUrl?=?url.Contains(monitorPath);
????????????System.Drawing.Image?imgSource?=?null;
????????????if?(!IsInterestUrl)??
????????????{
????????????????if?(!System.IO.File.Exists(context.Request.PhysicalPath))
????????????????????return;
????????????????imgSource?=?System.Drawing.Image.FromFile(context.Request.PhysicalPath);
????????????????imgSource.Save(context.Response.OutputStream,?imgSource.RawFormat);
????????????????imgSource.Dispose();
????????????????return;
????????????}?
????????????//圖片屬于封面，但圖片imageSource不存在，顯示默認圖片default.jpg
????????????string?physicalPath?=?context.Request.PhysicalPath;//?context.Server.MapPath(url);
????????????if?(!System.IO.File.Exists(physicalPath))
????????????{
????????????????string?defaultImage?=?System.Configuration.ConfigurationManager.AppSettings["defaultImage"];
????????????????imgSource?=?System.Drawing.Image.FromFile(context.Request.PhysicalApplicationPath?+?defaultImage);
????????????????imgSource.Save(context.Response.OutputStream,?imgSource.RawFormat);
????????????????imgSource.Dispose();
????????????????return;
????????????}
????????????//--===--------------------只要有封面圖片，就為圖片添加水印----------------------===---
????????????string?watermarkImage?=?System.Configuration.ConfigurationManager.AppSettings["watermarkImage"];
????????????string?watermarkImagePath?=?context.Request.PhysicalApplicationPath?+?watermarkImage;
????????????bool?bWatermarkImageExist?=System.IO.File.Exists(watermarkImagePath);
????????????imgSource?=?System.Drawing.Image.FromFile(physicalPath);
????????????System.Drawing.Graphics?graphic?=?System.Drawing.Graphics.FromImage(imgSource);
????????????if?(bWatermarkImageExist)?//“水印圖片”存在:存在則封面混合水印圖片
????????????{
????????????????System.Drawing.Image?imgWatermark?=?System.Drawing.Image.FromFile(watermarkImagePath);
????????????????graphic.DrawImage(imgWatermark,
????????????????????imgSource.Width?-?imgWatermark.Width,?imgSource.Height?-?imgWatermark.Height,
????????????????????imgWatermark.Width,?imgWatermark.Height);
????????????????//把圖片保存到輸出流
????????????????imgSource.Save(context.Response.OutputStream,?System.Drawing.Imaging.ImageFormat.Jpeg);
????????????????imgWatermark.Dispose();
????????????}
????????????else???????????????????????????????//“水印圖片”不存在:輸出文本
????????????{
????????????????System.Drawing.Font?font?=?new?System.Drawing.Font("幼圓",?13.0f,System.Drawing.FontStyle.Bold);
????????????????graphic.DrawString("第三波+書店",font?,?System.Drawing.Brushes.Red,?new?System.Drawing.PointF());
????????????????imgSource.Save(context.Response.OutputStream,?System.Drawing.Imaging.ImageFormat.Jpeg);
????????????}
????????????imgSource.Dispose();
????????????graphic.Dispose();
????????????//標明類型為jpg：如果不標注，IE沒有問題，但Firefox會出現亂碼
????????????context.Response.ContentType?=?"image/jpeg";
????????????context.Response.Flush();
????????????context.Response.End();
????????}
????}
}

轉載于:https://www.cnblogs.com/flaaash/archive/2007/12/23/1011640.html

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