sparency mask (see
the <a href="pgm.html">pgm format specification</a>).

<p>In a .ico file, there is no such thing as partial transparency
(translucency).  Where the PGM mask says completely opaque, the icon will
be opaque.  Everywhere else, the icon will be transparent.  Note that
as with any Netpbm program, you can use a PBM image for the transparency
mask and <b>ppmtowinicon</b> will treat it like a PGM.

<P>The and mask is like an alpha mask, except for what it signifies in
the "not opaque" areas.  In 