that expects
a true PPM, the display appears darker than it should, so
<B>pnmgamma</B> has the effect of lightening the image.  When you feed
a true PPM to a display program that expects linear sample values, and
therefore does a gamma correction of its own on them, the display
appears lighter than it should, so <B>pnmgamma</B> with a gamma value
less than one (the multiplicative inverse of whatever gamma value the
display program uses) has the effect of darkening the image.

<A NAME="lbAE">&nbsp;</A>
<H2>P