Resolving media urls in a virtual directory

Hi all,

I've got the following bit of XSLT for a marco.

<xsl:for-each select="$currentPage/* [@isDoc and string(umbracoNaviHide) != '1']">
<div class="photo">
  <xsl:variable name="thumb" select="umbraco.library:GetMedia(photo,0)/Image" />
  <img style="border:0px;" src="{$thumb/umbracoFile}" />   
</div>
</xsl:for-each>

My output for the image is:

<img style="border:0px;" src="~/media/278/kevinp.jpg">

How do I best resolve this to:

/brochure/media/278/kevinp.jpg

If i use umbraco.library.niceUrl(@id) for a page it works correctly.

Thanks,

Dan