colormapGMT creates colormaps in the Generic Mapping Tools (GMT)
scheme (see References 1 to 4). A few such schemes are built-in, and may be referred to
by name ("gmt_gebco", "gmt_globe", "gmt_ocean", or "gmt_relief")
while others are handled by reading local files that are in GMT
format, or URLs providing such files (see Reference 3).
colormapGMT(name, debug = getOption("oceDebug"))character value specifying the GMT scheme, or a source for such
a scheme. Four pre-defined schemes are available, accessed by setting name to
"gmt_gebco", "gmt_globe", "gmt_ocean", or "gmt_relief". If name is
not one of these values, then it is taken to be the name of a local file
in GMT format or, if no such file is found, a URL holding such a file.
integer that, if positive, indicates to print some debugging output
colormap returns a list, in the same format as the return value for colormap().
The GMT files understood by colormapGMT are what GMT calls
"Regular CPT files" (see reference 4). This is a text format that
can be read and (with care) edited in a text editor. There
are three categories of lines within this file. (1) Any
line starting with the "#" character is a comment, and is ignored
by colormapGMT. (2) Lines with 8 numbers specify colour bands.
The first number is a z value, and the three numbers after that
are red, green and blue values in the range from 0 to 255. This
set of 4 numbers is followed on the same line with similar values.
Think of this sequence as describing a band of colours between
two z values. (3) Lines starting with a character, followed
by three numbers, specify particular codings. The character "B"
specifies background colour, while "F" specifies foreground
colour, and "N" specifies the colour to be used for missing
data (the letter stands for not-a-number). Only "N" is used
by colormapGMT, and it takes on the role that the missingColor
argument would otherwise have. (This is why missingColor is not
permitted if name is given.)
General overview of GMT system https://www.generic-mapping-tools.org.
Information on GMT color schemes https://docs.generic-mapping-tools.org/dev/cookbook/cpts.html
Source of GMT specification files https://beamreach.org/maps/gmt/share/cpt/ (this link worked for years, but failed to respond in October 2021)
CPT (color palette table) format https://www.soest.hawaii.edu/gmt/gmt/html/GMT_Docs.html#x1-820004.15
Other things related to colors:
colormap(),
oceColors9B(),
oceColorsCDOM(),
oceColorsChlorophyll(),
oceColorsClosure(),
oceColorsDensity(),
oceColorsFreesurface(),
oceColorsGebco(),
oceColorsJet(),
oceColorsOxygen(),
oceColorsPAR(),
oceColorsPalette(),
oceColorsPhase(),
oceColorsSalinity(),
oceColorsTemperature(),
oceColorsTurbidity(),
oceColorsTurbo(),
oceColorsTwo(),
oceColorsVelocity(),
oceColorsViridis(),
oceColorsVorticity(),
ocecolors