In this case 446 lines, although that's the whole
ImageFileMaybeUploadWidget; the bit that does on-the-fly thumbnailing is
much smaller:

 //~ Inner Classes -------------------------------------------------

 /**
  * Separate out thumbnail generation into a separate class. The thumbnail
  * generator should generate thumbnails if the appropriate code is
  * present and should not break horribly if it is not. Note that
  * thumbnail generation does not work yet
  */
 class ThumbnailPainter
 {
   //~ Instance fields ---------------------------------------------

   /** can we generate? */
   private boolean canGenerate = true;

   //~ Methods -----------------------------------------------------

   /**
    * @return Returns the canGenerate.
    */
   public boolean getCanGenerate(  )
   {
     return canGenerate;
   }

   /**
    * maybe generate a thumbnail for this source. Why maybe?  Well, of
    * course, if the appropriate library isn't available we can't.
    *
    * @param context the service context in which this generation takes
    *       place
    * @param the name of the value being processed
    * @param source the source file from which to generate the thumbnail
    * @param prefix the string to prepend to the name of the source file
    *       to construct the name of the thumbnail file
    * @param maxWidth the maximum width of the thumbnail image
    * @param maxHeight the maximum height of the thumbnail image
    *
    * @exception IOException if it busts.
    */
   protected File maybeGenerate( Context context, String name,
     File source, String prefix, int maxWidth, int maxHeight )
     throws IOException
   {
     File result = null;

     if ( canGenerate && ( source != null ) )
     {
       String thumbName =
         source.getParent(  ) + File.separator + prefix +
         source.getName(  );

       result = new File( thumbName );

       if ( !result.exists(  ) )
       {
         BufferedImage image = ImageIO.read( source );
         
         ImageObserver observer = new Canvas(  );

         int height = image.getHeight( observer );
         int width = image.getWidth( observer );

         context.put( name +
           ImageFileMaybeUploadWidget.IMAGEHEIGHTSUFFIX, height );
         context.put( name +
           ImageFileMaybeUploadWidget.IMAGEWIDTHSUFFIX, width );

         if ( height > width )
         {
           width =
             (int) ( (float) maxWidth * (float) ( (float) width / (float)
height ) );
           height = maxHeight;
         }
         else
         {
           height =
             (int) ( (float) maxHeight * (float) ( (float) height /
(float) width ) );
           width = maxWidth;
         }

         context.put( name +
           ImageFileMaybeUploadWidget.THUMBHEIGHTSUFFIX, height );
         context.put( name +
           ImageFileMaybeUploadWidget.THUMBWIDTHSUFFIX, width );

         Image thumb =
           image.getScaledInstance( width, height,
             Image.SCALE_SMOOTH );

         BufferedImage buff =
           new BufferedImage( width, height,
             BufferedImage.TYPE_INT_BGR );
         buff.createGraphics(  ).drawImage( thumb, 0, 0, observer );

         System.err.println( "Writing thumbnail to " + thumbName );

         if ( thumbName.toLowerCase().endsWith( ".gif" ) )
         {
           ImageIO.write( buff, "GIF", result );
         }
         else if ( thumbName.toLowerCase().endsWith( ".jpg" ) )
         {
           ImageIO.write( buff, "JPEG", result );
         }
         else
         {
           throw new IOException(
             "Can't create a thumbnail from " +
             source.getName(  ) );
         }
       }
     }

     return result;
   }
 }