wmf files are often stored compressed compressed with lz compression in 
word files

<quote from documentation>
They are normally stored in a compressed format using the LZ compression
algorithm in the format used by GNU Zip deflate/inflate with a 32k window.
The format is zlib format . The only metafile compression version number
currently defined identifies this format and is analogous to the PNG
compression type value in the PNG file format.
</quote>

Peter Brandstrom - D/Z <peter.brandstrom@ericsson.com> took at look at it
and said
<quote>
The compressed data begins with a zlib header which seems to be two
bytes containing the compression method, window size and check byte. The
zlib default is a 32k window.
</quote>
