The TVLCT procedure loads the display color translation tables from the specified variables. Although IDL uses the RGB color system internally, color tables can be specified to TVLCT using any of the following color systems: RGB (Red, Green, Blue), HLS (Hue, Lightness, Saturation), and HSV (Hue, Saturation, Value). Alpha values may also be used when using the second form of the command. The type and meaning of each argument is dependent upon the color system selected, as described below. Color arguments can be either scalar or vector expressions. If no color-system keywords are present, the RGB color system is used. See Image Display Routines for a more complete explanation of color systems.
TVLCT will accept either three n -element vectors ( V 1 , V 2 , and V 3 ) or a single n by 3 array ( V ) as an argument. The vectors (or columns of the array) have different meanings depending on the color system chosen. If an array V is specified, V [*,0] is the same as V 1 , V [*,1] is the same as V 2 , V [*,2] is the same as V 3 . In the description below, we assume that three vectors, V 1 , V 2 , and V 3 are specified.
The parameters V 1 , V 2 , and V 3 contain the Red, Green, and Blue values, respectively. Values are interpreted as integers in the range 0 (lowest intensity) to 255 (highest intensity). The parameters can be scalars or vectors of up to 256 elements. By default, the three arguments are assumed to be R, G, and B values.
Parameters V 1 , V 2 , and V 3 contain the Hue, Lightness, and Saturation values respectively. All parameters are floating-point. Hue is expressed in degrees and is reduced modulo 360. V 2 (lightness) and V 3 (saturation) and can range from 0 to 1.0. Set the HLS keyword to have the arguments interpreted this way.
Parameters V 1 , V 2 , and V 3 contain values for Hue, Saturation, and Value (similar to intensity). All parameters are floating-point. Hue is in degrees. The Saturation and Value can range from 0 to 1.0. Set the HSV keyword to have the arguments interpreted this way.