ty value.  The <b>-invert</b> option does not apply to this
opacity value.

<p>As a simple opacity value, the value makes sense only if it is
between 0 and 1, inclusive.  However, <b>pamcomp</b> accepts all
values and performs the same arithmetic computation using whatever
value you provide.  An opacity value less than zero means the underlay
image is intensified and then the overlay image is "subtracted" from
it.  An opacity value greater than unity means the overlay image is
intensified and the underlayin