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

using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Web.SessionState;

public class Thumb : IHttpHandler, IRequiresSessionState
{
  bool ThumbnailCallback()
  {
    return false;
  }

    public bool IsReusable
    {
        get { return false; }
    }

    
    
    
    public void ProcessRequest(HttpContext context)
    {
        Image.GetThumbnailImageAbort callback = new Image.GetThumbnailImageAbort(ThumbnailCallback);

        Bitmap bmp;
        Image thumb;
 
        string file = string.Empty;
        string path = context.Server.MapPath("./" + context.Request.QueryString["nomefile"]);

        
        //--- dimensioni della thubnail
        double width = 100;
        double height = 100;


    
        bmp = new Bitmap(path);

        width = bmp.Width;
        height = bmp.Height;

        //--- calcolo le proporzioni
        if (bmp.Width > width)
        { 
            double prop = width/bmp.Width;
            height = (int)(prop * bmp.Height);
        }

        
    //--- creo la thumbnail con quelle dimensioni
        thumb = bmp.GetThumbnailImage(width, height, callback, IntPtr.Zero);

        
        //--- scrivo negli header che è un'immagine
        context.Response.AddHeader("Content-Type", "image/jpeg");
        thumb.Save(context.Response.OutputStream, ImageFormat.Jpeg);
        thumb.Dispose();
        bmp.Dispose();
    }

}