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[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.
Load the default color table.
Load a color table with a circular hue value, from red to red.
Load a color table from dark blue to light blue, white, light red,
dark red, suited for blueshift to redshift display.
Load a black and white color table (white background, black
- 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).
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
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-
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
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,