makecpt
makecpt - Make GMT color palette tables
Synopsis
makecpt [ -A[+]transparency ]
[ -Ccpt ]
[ -D[i|o] ]
[ -E[nlevels] ]
[ -F[R|r|h|c ]
[ -Gzlo/zhi ]
[ -I ] [ -M ]
[ -N ] [ -Q[i|o] ]
[ -Tz_min/z_max[/z_inc[+]] | -Tztable ]
[ -V[level] ] [ -W ] [ -Z ]
Note: No space is allowed between the option flag and the associated arguments.
Description
makecpt is a utility that will help you make color palette tables
(CPT files). You define an equidistant set of contour intervals or pass
your own z-table, and create a new CPT file based on an existing master
CPT file. The resulting CPT file can be reversed relative to the master
cpt, and can be made continuous or discrete. For color tables beyond the
standard GMT offerings, visit cpt-city:
http://soliton.vm.bytemark.co.uk/pub/cpt-city/.
The CPT file includes three additional colors beyond the range of
z-values. These are the background color (B) assigned to values lower
than the lowest z-value, the foreground color (F) assigned to values
higher than the highest z-value, and the NaN color (N) painted
wherever values are undefined.
If the master CPT file includes B, F, and N entries, these will be
copied into the new master file. If not, the parameters
COLOR_BACKGROUND, COLOR_FOREGROUND,
and COLOR_NAN from
the gmt.conf file or the command line will be used. This default
behavior can be overruled using the options -D, -M or -N.
The color model (RGB, HSV or CMYK) of the palette created by makecpt
will be the same as specified in the header of the master CPT file. When
there is no COLOR_MODEL entry in the master CPT file, the
COLOR_MODEL specified in the gmt.conf file or on the command
line will be used.
Optional Arguments
- -A[+]transparency
- Sets a constant level of transparency (0-100) for all color slices.
Prepend + to also affect the fore-, back-, and nan-colors
[Default is no transparency, i.e., 0 (opaque)].
- -Ccpt
- Selects the master color table CPT file to use in the interpolation.
Choose among the built-in tables (type makecpt to see the list)
or give the name of an existing CPT file [Default gives a rainbow CPT file].
Yet another option is to specify -Ccolor1,color2[,color3,...]
to build a linear continuous cpt from those colors automatically.
In this case colorn can be a r/g/b triplet, a color name,
or an HTML hexadecimal color (e.g. #aabbcc ).
- -D[i|o]
- Select the back- and foreground colors to match the colors for
lowest and highest z-values in the output CPT file [Default uses
the colors specified in the master file, or those defined by the
parameters COLOR_BACKGROUND, COLOR_FOREGROUND, and
COLOR_NAN]. Append i to match the colors for the lowest and
highest values in the input (instead of the output) CPT file.
- -E[nlevels]
- Implies reading data table(s) from given command-line files or standard input.
We use the last data column to determine the data range; use -i to
select another column, and use -bi if your data table is native binary.
This z-range information is used instead of providing the -T option.
We create a linear color table by dividing the table data z-range into
nlevels equidistant slices. If nlevels is not given it defaults to
the number of levels in the chosen CPT file.
- -F[R|r|h|c]
- Force output CPT file to written with r/g/b codes, gray-scale values
or color name (R, default) or r/g/b codes only (r), or h-s-v
codes (h), or c/m/y/k codes (c).
- -Gzlo/zhi
- Truncate the incoming CPT so that the lowest and highest z-levels
are to zlo and zhi. If one of these equal NaN then
we leave that end of the CPT alone. The truncation takes place
before any resampling.
- -I
- Reverses the sense of color progression in the master CPT file. Also
exchanges the foreground and background colors, including those
specified by the parameters COLOR_BACKGROUND and
COLOR_FOREGROUND.
- -M
- Overrule background, foreground, and NaN colors specified in the
master CPT file with the values of the parameters
COLOR_BACKGROUND, COLOR_FOREGROUND,
and COLOR_NAN
specified in the gmt.conf file or on the command line. When
combined with -D, only COLOR_NAN is considered.
- -N
- Do not write out the background, foreground, and NaN-color fields [Default will write them].
- -Q[i|o]
- Selects a logarithmic interpolation scheme [Default is linear].
-Qi expects input z-values to be log10(z), assigns colors, and
writes out z [Default]. -Qo takes log10(z) first, assigns
colors, and writes out z.
- -Tz_min/z_max[/z_inc[+]] | -Tztable
- Defines the range of the new CPT file by giving the lowest and
highest z-value and interval. When used with -C and z_inc is
not specified, the number of intervals remains the same as in the
input palette. If z_inc is specified with a trailing + we
interpret z_inc as the number of desired intervals instead.
Alternatively, give the name of a ASCII file that has one z-value
per record. If -T is not given, the existing range in the master
CPT file will be used intact.
- -V[level] (more ...)
- Select verbosity level [c].
- -W
- Do not interpolate the input color table but pick the output colors
starting at the beginning of the color table, until colors for all
intervals are assigned. This is particularly useful in combination
with a categorical color table, like “categorical”. Cannot be used
in combination with -Z.
- -Z
- Creates a continuous CPT file [Default is discontinuous, i.e.,
constant colors for each interval].
- -^ or just -
- Print a short message about the syntax of the command, then exits (NOTE: on Windows use just -).
- -+ or just +
- Print an extensive usage (help) message, including the explanation of
any module-specific option (but not the GMT common options), then exits.
- -? or no arguments
- Print a complete usage (help) message, including the explanation of
options, then exits.
- --version
- Print GMT version and exit.
- --show-datadir
- Print full path to GMT share directory and exit.
Examples
To make a CPT file with z-values from -200 to 200, with discrete color
changes every 25, and using a polar blue-white-red colortable:
gmt makecpt -Cpolar -T-200/200/25 > colors.cpt
To make an equidistant CPT file from z = -2 to 6, in steps of 1, using
continuous default rainbow colors:
gmt makecpt -T-2/6/1 -Z > rainbow.cpt
To make a GEBCO look-alike CPT file for bathymetry, run
gmt makecpt -Cgebco > my_gebco.cpt
To create a 24-level rainbow color table suitable for plotting the depths in
the data table depths.txt (with lon, lat, depths), run
gmt makecpt -Cgebco depths.txt -i2 -Z -E24 > my_depths.cpt
Bugs
Since makecpt will also interpolate from any existing CPT file you
may have in your directory, you cannot use one of the listed cpt names
as an output filename; hence the my_gebco.cpt in the example.