View source for center an external image

Reviewing the documentation I found the following to resize and center an image:
%%(code)(( width=500 align=center))%% 
I used this a lot:
%%(code) %(wacko wrapper=text wrapper_align=center)(( %%
the bad thing is that it is mandatory to use the size, that is I can't just center the image.
%%(code)(( align=center))%% 
Is there another way to do it?