Warning: This function is
currently not documented; only the argument list is
available.
Warning: This function is
EXPERIMENTAL. The behaviour of this function, the
name of this function, and anything else documented about this
function may change without notice in a future release of PHP.
Use this function at your own risk.
Applys an arithmetic, relational, or logical expression to an image. Use
these operators to lighten or darken an image, to increase or decrease
contrast in an image, or to produce the "negative" of an image.
Return Values
Returns TRUE
on success.