public class ImageHandler : IHttpHandler
{
    // the max size of the Thumbnail
    const int MaxDim = 120;

    public void ProcessRequest(HttpContext ctx)
    {
        // let's cache this for 1 day
        ctx.Response.ContentType = "image/jpeg";
        ctx.Response.Cache.SetCacheability(HttpCacheability.Public);
        ctx.Response.Cache.SetExpires(DateTime.Now.AddDays(1));

        // find the directory where we're storing the images
        string imageDir = ConfigurationSettings.AppSettings["imageDir"];
        imageDir = Path.Combine(
            ctx.Request.PhysicalApplicationPath, imageDir);

        // find the image that was requested
        string file = ctx.Request.QueryString["File"];
        file = Path.Combine(imageDir, file);
        // load it up
        using (Image img = new Bitmap(file))
        {
            // do some math to resize the image
            // note: i know very little about image resizing,
            // but this just seemed to work under v1.1. I think
            // under v2.0 the images look incorrect.
            // *note to self* fix this for v2.0
            int h = img.Height;
            int w = img.Width;
            int b = h > w ? h : w;
            double per = (b > MaxDim) ? (MaxDim * 1.0) / b : 1.0;
            h = (int)(h * per);
            w = (int)(w * per);

            // create the thumbnail image
            using (Image img2 =
                      img.GetThumbnailImage(w, h,
                      new Image.GetThumbnailImageAbort(Abort),
                      IntPtr.Zero))
            {
                // emit it to the response strea,
                img2.Save(ctx.Response.OutputStream,
                    System.Drawing.Imaging.ImageFormat.Jpeg);
            }
        }
    }

    public bool IsReusable
    {
        get { return true; }
    }

    private bool Abort()
    {
        return false;
    }
}