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>
    /// 图片处理模块：给指定路径下的图片添加水印输出
    /// 1.监视的目录路径，水印图片路径，默认图片三者都在web.config文件中设定
    /// 2.请求的图片的路径不属于监视路径，直接输出图片
    /// 3.请求的图片的路径属于监视路径，若图片不存在，显示默认图片，不加水印
    /// 4.请求的图片的路径属于监视路径，且文件存在，添加水印
    ///        水印图片存在：图片+水印图片，输出
    ///        水印图片不存在：图片+水印文字，输出
    ///        
    /// 5.web.config部分如下：
    ///         <appSettings>
    ///                  <!--要监视的路径-->
    ///                     <add key="monitorPath" value="/images/bookcovers/"/>
    ///                 <!--图书封面不存在时显示的默认封面图片的相对路径-->
    ///                    <add key="defaultImage" value="images\default.jpg"/>
    ///                 <!--相对于物理应用程序的根路径的水印图片的相对路径-->
    ///                      <add key="watermarkImage" value="images\WaterMark.jpg"/>
    ///        </appSettings>
    ///     
    ///         <httpHandlers>
    ///                <add verb="*" path="*.jpg" type="xumh.WatermarkHandler,WatermarkHandler"/>
    ///            </httpHandlers>
    ///       许明会  2007-12-23 18:00 Visual Studio 2005 调试通过
    /// </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"];
            //若图片不属于封面，直接输出图片:若图片不存在不做处理
            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;
            } 
            //图片属于封面，但图片imageSource不存在，显示默认图片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;
            }
            //--===--------------------只要有封面图片，就为图片添加水印----------------------===---
            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) //“水印图片”存在:存在则封面混合水印图片
            {
                System.Drawing.Image imgWatermark = System.Drawing.Image.FromFile(watermarkImagePath);
                graphic.DrawImage(imgWatermark,
                    imgSource.Width - imgWatermark.Width, imgSource.Height - imgWatermark.Height,
                    imgWatermark.Width, imgWatermark.Height);
                //把图片保存到输出流
                imgSource.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                imgWatermark.Dispose();
            }
            else                               //“水印图片”不存在:输出文本
            {
                System.Drawing.Font font = new System.Drawing.Font("幼圆", 13.0f,System.Drawing.FontStyle.Bold);
                graphic.DrawString("第三波+书店",font , System.Drawing.Brushes.Red, new System.Drawing.PointF());
                imgSource.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            imgSource.Dispose();
            graphic.Dispose();
            //标明类型为jpg：如果不标注，IE没有问题，但Firefox会出现乱码
            context.Response.ContentType = "image/jpeg";
            context.Response.Flush();
            context.Response.End();
        }
    }
}