SWAP

        SWAP

    This  task  swaps  an  image  with respect to first or second axis (e.g.
    along  the  X dimension, pixel 1 becomes pixel NX, 2 becomes NX-1 and so
    on).  This operation is never required for most algorithms because  they
    work  in  the "User Coordinate" space (such as the contouring command in
    GRAPHIC...).  It is only needed for a few algorithms which work  in  the
    pixel  space (such as HISTO_CROSS).  Pixel order can be reversed along X
    (first axis) or Y (second axis).  The program does not handle data cubes
    at present..