ASP.NET中图片显示方法实例

// Copyright (C) 2003 by Greg Ennis
// (mailto:greg@ennis.net)
//
// The contents of this file are subject to the Artistic License (the "License").
// You may not use this file except in compliance with the License. 
// You may obtain a copy of the License at:
// http://www.opensource.org/licenses/artistic-license.html
using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Web;
using System.IO;
using System.Configuration;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
namespace netpix
{
  public class ImageGenerator : IHttpHandler 
  { 
    public bool IsReusable 
    { get { return true; } } 
    public void ProcessRequest(HttpContext Context) 
    { 
      // Get the image filename and album root path from the database
      //图片浏览次数
      int numviews;
      //图片数据库中的ID
      int picid = Convert.ToInt32(Context.Request["id"]);
      //图片路径　
      string imgpath = npdata.GetPathToPicture(picid, out numviews);
      // Writing an image to output stream
      Context.Response.ContentType = "image/jpg";
      // 'thumbnail' means we are requesting a thumbnail
      //显示缩略图
      if (Context.Request["thumbnail"] != null)
      {
        // Need to load the image, resize it, and stream to the client.
        // Calculate the scale so as not to stretch or distort the image.
        Bitmap bmp = new Bitmap(imgpath);
        float scale = 150.0f / System.Math.Max(bmp.Height, bmp.Width);
        System.Drawing.Image thumb = bmp.GetThumbnailImage((int)(bmp.Width * scale), (int)(bmp.Height * scale), null, System.IntPtr.Zero);
        thumb.Save(Context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
        bmp.Dispose();
        thumb.Dispose();
      }
      else
      {
        // Stream directly from the file
        // Get the stream and send it out the response
        System.IO.FileStream fs = File.Open(imgpath, FileMode.Open, FileAccess.Read, FileShare.Read);
        const int byteLength = 8192;
        byte[] bytes = new byte[byteLength];
        while( fs.Read(bytes, 0, byteLength ) != 0 )
        {
          Context.Response.BinaryWrite(bytes); 
        }
        fs.Close();
        //更新数据库浏览次数
        npdata.SetNumViews(picid, numviews+1);
      }
    }
  }
}