LUT

        [GTVL\]LUT [Argum] [/PEN] [/REVERSE]

    Modify the bitmap or pen look up table. Option /PEN indicates to  modify
    the  value  of the 16 user-controlled pen colors (colors 8 to 23) rather
    than the bitmap look-up table.

    The default argument is LUT. Possibles arguments are:
    - ?
        Type "LUT ?" to display the list of available LUTs. One can use  al-
        ternatively  the  LUT  editor (button "Edit Lut") to browse and edit
        the LUTs in an interactive widget.
    - DEFAULT
        Load the default color table.
    - COLOR
        Load a color table with a circular hue value, from red to red.
    - BLACK
        Load  a  black  and  white  color  table  (white  background,  black
        sources).
    - WHITE, RED, GREEN, BLUE, MAGENTA, YELLOW, CYAN and NULL
        Load  a  color table with black background and sources in the corre-
        sponding color (NULL is fully black).
    - LUT
        Load the color table defined by an HSV (HUE, SATURATION  and  VALUE)
        or  RGB (RED, GREEN and BLUE) color model. There are six user-write-
        able SIC variables named  LUT%HUE,  LUT%SATURATION,  LUT%VALUE,  and
        LUT%RED,  LUT%GREEN  and LUT%BLUE that contain the HSV and RGB model
        of the current LUT. These arrays values  can  be  manipulated  using
        standard  SIC mathematic functions to create new Look-Up Tables (see
        below). Depending on the value on LUT%MODE, the model is  read  from
        the HSV (LUT%MODE.eq.1) or from the RGB (LUT%MODE.eq.2) arrays.
    - Any other LUT Argum will read Red Green Blue values from the formatted
        file named "Argum". See subtopic FILE for details.

    A convenient value for the hue array is
            LET LUT%HUE[I] = 256*(1-(I/LUT%SIZE))
            LET LUT%SATURATION 1
            LET LUT%VALUE 1
            LUT LUT
    which is a "classical" color table from blue to red as used in AIPS  for
    example. Color contours can be obtained using variations around the fol-
    lowing command:
            LET LUT%HUE[I] = 16*INT(256*(1-(I/LUT%SIZE))/16)
    and so on with the most funny functions you may invent.
    CAUTION: the hue is a real number between 0.0 and 360.0

    The LUT, whereever it comes from, can be reverted before  use  with  the
    option /REVERSE.

    Note  that  a  similar  behaviour is defined for the BLANKING color (the
    color used to paint blanked  pixels  in  images),  with  the  six  reals
    LUT%BLANK%HUE, LUT%BLANK%SATURATION, LUT%BLANK%VALUE, and LUT%BLANK%RED,
    LUT%BLANK%GREEN, LUT%BLANK%BLUE.