LUT
Keywords: greg

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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, or execute the
            demonstration procedure @ gag_demo:demo-luts.greg for  an  overview.
            One  can  use  alternatively  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.
        - BLUERED
            Load a color table from dark blue to light blue, white,  light  red,
            dark red, suited for blueshift to redshift display.
        - 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.

Subsections

- LUT /PEN
- LUT FILE
- LUT CET