Color palettes require terminal entries for filled color polygons and palettes of smooth colors, are currently available for terminals listed in help for set pm3d. The range of color values are adjustable independently by set cbrange and set log cb. The whole color palette is visualized in the colorbox.
Syntax:
set palette set palette { { gray | color } { gamma <gamma> } { rgbformulae <r>,<g>,<b> | defined { ( <gray1> <color1> {, <grayN> <colorN>}... ) } | file '<filename>' {datafile-modifiers} | functions <R>,<G>,<B> } { model { RGB | HSV | CMY | YIQ | XYZ } } { positive | negative } { nops_allcF | ps_allcF } { maxcolors <maxcolors> } } show palette show palette palette <n> {{float | int}} show palette gradient show palette fit2rgbformulae show palette rgbformulae show colornames
set palette (i.e. without options) sets up the default values. Otherwise, the options can be given in any order. show palette shows the current palette properties.
show palette gradient displays the gradient defining the palette (if
appropriate). show palette rgbformulae prints the available fixed gray -
color transformation formulae. show colornames prints the known color names.
show palette palette n
prints to the screen or to the file given by
set print a table of RGB triplets calculated for the current palette settings
and a palette having
n
discrete colors. The default wide table can be
limited to 3 columns of r,g,b float values [0..1] or integer values [0..255]
by options float or int, respectively. This way, the current gnuplot color
palette can be loaded into other imaging applications, for example Octave.
Additionally to this textual list of RGB table, you can use the test palette
command to plot the R,G,B profiles for the current palette.
The following options determine the coloring properties.
Figure using this palette can be gray or color. For instance, in pm3d
color surfaces the gray of each small spot is obtained by mapping the averaged
z-coordinate of the 4 corners of surface quadrangles into the range
[min_z,max_z] providing range of grays [0:1]. This value can be used directly
as the gray for gray maps. The color map requires a transformation gray -
(R,G,B), i.e. a mapping [0:1] -
([0:1],[0:1],[0:1]).
Basically two different types of mappings can be used: Analytic formulae to convert gray to color, or discrete mapping tables which are interpolated. palette rgbformulae and palette functions use analytic formulae whereas palette defined and palette file use interpolated tables. palette rgbformulae reduces the size of postscript output to a minimum.
The command show palette fit2rgbformulae finds the best matching set palette rgbformulae for the current set palette. Naturally, it makes sense to use it for non-rgbformulae palettes. This command can be found useful mainly for external programs using the same rgbformulae definition of palettes as gnuplot, like zimg (
http://zimg.sourceforge.nethttp://zimg.sourceforge.net
).
set palette gray switches to a gray only palette. set palette rgbformulae, set palette defined, set palette file and set palette 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 gamma
can be done for
gray maps only (set palette gray). Linear mapping to gray is for gamma
equals 1, see test palette (p.
). 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 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 set palette 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:
http://en.wikipedia.org/wiki/Color_spacehttp://en.wikipedia.org/wiki/Color_space