Using different image format given the export backend

[Garrido Xavier <garrido@lal.in2p3.fr>]

Dear Orgers,

As explain is this forum thread 
http://stackoverflow.com/questions/13611837/how-can-i-use-different-image-formats-for-different-exports-in-org-mode, 
I'd also like to use different image format given the export backend. I 
have used the answer provided in the forum to have something like that

#+CAPTION: Toto figure
#+NAME: fig::toto
#+ATTR_LATEX: :width 0.38\textwidth
#+BEGIN_SRC emacs-lisp :exports results :results value raw
   (case (and (boundp 'backend) backend)
     (nil "")
     (latex "[[file:./toto.pdf]]"
     (html  "[[file:./toto.png]]"))
#+END_SRC

While the export is fine with html, when I export to latex->pdf, it 
gives me :

\includegraphics[width=.9\linewidth]{./toto.pdf}

not respecting the latex width attribute nor caption. I am using the new 
exporter and I wonder if I can get something working in the same way.

Thanks a lot for your help,
Xavier
-- 

   |
   |__     GARRIDO Xavier       Laboratoire de l'Accélérateur Linéaire
    /\     NEMO                 Université Paris-Sud 11
   /--\    garrido@lal.in2p3.fr UMR 8607
   |       garrido@in2p3.fr     Batiment 200
   |__     +33 1.64.46.84.28    91898 Orsay Cedex, France