[NTG-context] height and width of a figure

hi all i included an external figure in a document with \useexernalfigure[fig] how can i get the width and the height of this picture so that i can make a frame that has exactly the same size as the externalfigure[fig]. thanks a lot for help greetings severin -- +++ GMX - die erste Adresse für Mail, Message, More! +++ Getestet von Stiftung Warentest: GMX FreeMail (GUT), GMX ProMail (GUT) (Heft 9/03 - 23 e-mail-Tarife: 6 gut, 12 befriedigend, 5 ausreichend) Jetzt selbst kostenlos testen: http://www.gmx.net