<graphic> scaling

I have several diagrams (= png files) which I want to display in DocBook.
I want them to have the width of the surrounding text ("100%").

Is it possible to arrange for that?

In XHTML rendered by Mozilla I can check an option "scale images to fit
the screen", but what do I do with FO?

I tried playing with scale="50" and scalefit="1" &c,
but that does not buy anything
(i.e., the graphic is smaller than it should be).
Also, <graphic> is going to be removed in 5.0,
so how is this going to be handled then?

--
Sam Steingold (http://www.podval.org/~sds) running w2k
<http://www.camera.org> <http://www.iris.org.il> <http://www.memri.org/>
<http://www.mideasttruth.com/> <http://www.honestreporting.com>
If Perl is the solution, you're solving the wrong problem. - Erik Naggum