EPS/PDF import and \underbrace in metaplay

[Mojca Miklavec <mojca.miklavec1@email.si>]

I have two questions cencerning metapost/metaplay:

1.) EPS/PDF import

How do I make an existing EPS or PDF image a part of some other 
meta[post/play] graphic?

2.) \underbrace

I wrote the following two macros for drawing braces in graphics:

\def\underbracedescription#1#2{$\underbrace{\hbox{\vrule width#1 height
0bp}}_{\hbox{\strut #2}}$}
\def\rightbracedescription#1#2{$\displaystyle{\left.\vphantom{\hbox{\vrule
width0bp height#1 depth#1}}\right\}\hbox{\strut #2}}$}

However, the width has to be given manually - it doesn't care about the
actual size of the object it has to be applied to. How is it possible to
give the command some more flexibility?
(say, to be able to simply use 
\underbracedescription{pict}{description}, perhaps even without the need 
of specifying the coordinates explicitly, but)

Thanks a lot,
	Mojca Miklavec