GNUPlot Manual

86 gnuplot 4.0 36 SET-SHOW
set palette gray switches to a gray only palette. rgbformulae, defined, file and functions switch
to a color mapping. set palette color is an easy way to switch back from the gray palette to the last
color mapping.
Automatic gamma correction via set palette gamma can be done for gray maps only (set
palette gray). Linear mapping to gray is for gamma equals 1, see test palette (p. 158). Gamma is
ignored for color mappings.
Most terminals support only discrete number of colors (e.g. 256 colors in gif). All entries of the palette
remaining after the default gnuplot linetype colors declaration are allocated for pm3d by default. Then
multiplot could fail if there are no more color positions in the terminal available. Then you should use
set palette maxcolors with a reasonably small value. This option can also be used to
separate levels of z=constant in discrete steps, thus to emulate filled contours. Default value of 0 stays
for allocating all remaining entries in the terminal palette or for to use exact mapping to RGB.
RGB color space might not be the most useful color space to work in. For that reason you may change
the color space with model to one of RGB, HSV, CMY, YIQ and XYZ. Using color names for
defined tables and a color space other than RGB will result in funny colors. All explanation have been
written for RGB color space, so please note, that R can be H, C, Y, or X, depending on the actual
color space (G and B accordingly).
All values for all color spaces are limited to [0,1].
RGB stands for Red, Green and Blue; CMY stands for Cyan, Magenta and Yellow; HSV stands for
Hue, Saturation, and Value; YIQ is the color model used by the U.S. Commercial Color Television
Broadcasting, it is basically an RGB recoding with downward compatibility for black and white television;
XYZ are the three primary colors of the color model defined by the ’Commission Internationale de
l’Eclairage’ (CIE). For more information on color models see:
and
http://www.cs.rit.edu/~ ncs/color/glossary.htm
http://cs.fit.edu/wds/classes/cse5255/cse5255/davis/index.html
36.49.1 Rgbformulae
For rgbformulae three suitable mapping functions have to be chosen. This is done via rgbformulae
,,. The available mapping functions are listed by show palette rgbformulae. Default
is 7,5,15, some other examples are 3,11,6, 21,23,3 or 3,23,21. Negative numbers, like 3,-11,-6, mean
inverted color (i.e. 1-gray passed into the formula, see also positive (p. 86) and negative (p. 86)
options below).
Some nice schemes in RGB color space
7,5,15 ... traditional pm3d (black-blue-red-yellow)
3,11,6 ... green-red-violet
23,28,3 ... ocean (green-blue-white); try also all other permutations
21,22,23 ... hot (black-red-yellow-white)
30,31,32 ... color printable on gray (black-blue-violet-yellow-white)
33,13,10 ... rainbow (blue-green-yellow-red)
34,35,36 ... AFM hot (black-red-yellow-white)
A full color palette in HSV color space
3,2,2 ... red-yellow-green-cyan-blue-magenta-red
Please note that even if called rgbformulae the formulas might actually determine the ,,
or ,, or ... color components as usual.
Use positive and negative to invert the figure colors.
Note that it is possible to find a set of the best matching rgbformulae for any other color scheme by the
command
show palette fit2rgbformulae