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.
Returns the index of the current active image within the Imagick object.
Return Values
Returns an integer containing the index of the image in the stack,
throwing ImagickException on error.