Look-Up Tables

Look-up tables or LUTs are the tables that map the data in the image memory into colours on the display when the system is used in PseudoColor mode.
In contrast to hardware display systems, the size of the LUT is not constant but depends upon how many colors are already used by other X applications running already. If less colors than a given LUTmin value are available, a so called private LUT is generated. This LUT is then only applicable when the focus is in that display window, changing the colors of all other windows in a nice psychedelic way (the LUTmin value is specified in the INITIALIZE/DISPLAY command).  
Commands exist to load LUTs into the image display, to modify the LUTs interactively and to read back LUTs from the image display.
 
In RGB mode the unique LUT used is a ramp in the three colors.
 
Some of the existing LUTs for PseudoColor mode are:

backgr
color
heat
idl4, idl5, ...4, idl5, ... !inspired by the IDL system
light
pastel
pseudo1, pseudo2
rainbow, rainbow1 ... rainbow4
random, random1 ... random4
smooth
staircase
stairs8

Use the command TUTORIAL/LUT to see how some of the available LUTs actually look like and how to modify a LUT interactively.
 
The main commands associated with LUTs are:
 
LOAD/LUT - load a look-up table
GET/LUT - read back a look-up table
MODIFY/LUT - interactively modify a look-up table
CLEAR/LUT - bypass the look-up table
SET/LUT - pass through a look-up table
DISPLAY/LUT - show the look-up table as a colour bar
CREATE/LUT - create a look-up table using the HSI colour model
 
Via the MIDAS application procedure (i.e. a procedure executed via the MIDAS command @a) vertlut.prg you can display the active LUT in a vertical bar at the left/right of the window with tick marks and intensities.
 
Commands like MODIFY/LUT need a displacement. Use the arrow keys to move left, right and down (to thin) or up (to thicken) a colour bar. Again the speed of the movements is controlled via the keys 0, 1, ..., 9.