Provided by: gmt-common_5.4.3+dfsg-1_all 
NAME
makecpt - Make GMT color palette tables
SYNOPSIS
makecpt [ -A[+]transparency ] [ -Ccpt ] [ -D[i|o] ] [ -E[nlevels] ] [ -F[R|r|h|c ][+c]] [ -Gzlo/zhi
] [ -I[c][z] ] [ -M ] [ -N ] [ -Q[i|o] ] [ -Tz_min/z_max[/z_inc[+]] | -Tztable | -Tz1,z2,…,zn ] [
-V[level] ] [ -W[w] ] [ -Z ] [ -bibinary ] [ -dinodata ] [ -iflags ]
Note: No space is allowed between the option flag and the associated arguments.
DESCRIPTION
makecpt is a utility that will help you make static color palette tables (CPTs). You define an
equidistant set of contour intervals or pass your own z-table or list, and create a new CPT based on an
existing master (dynamic) CPT. The resulting CPT 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 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 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. When there is no COLOR_MODEL entry in the master CPT, the COLOR_MODEL specified
in the gmt.conf file or on the command line will be used.
REQUIRED ARGUMENTS
None.
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 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 [Default gives a rainbow CPT].
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 [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.
-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.
-F[R|r|h|c][+c]]
Force output CPT 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). Optionally or alternatively,
append +c to write discrete palettes in categorical format.
-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. See also manipulating_CPTs
-I[c][z]
Append c [Default] to reverse the sense of color progression in the master CPT. Also exchanges the
foreground and background colors, including those specified by the parameters COLOR_BACKGROUND and
COLOR_FOREGROUND. Append z to reverse the sign of z-values in the color table. Note that this
change of z-direction happens before -G and -T values are used so the latter much be compatible
with the changed z-range. See also manipulating_CPTs
-M Overrule background, foreground, and NaN colors specified in the master CPT 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 | -Tz1,z2,…,zn
Defines the range of the new CPT by giving the lowest and highest z-value and interval. Append
/z_inc to sample the input CPT discretely at intervals z_inc between z_min and z_max; append a
trailing + to 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, or provide a list of comma-separated
z-values instead. If -T is not given, the existing range in the master CPT will be used intact.
-V[level] (more …)
Select verbosity level [c].
-W[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. Alternatively, use -Ww to produce a wrapped (cyclic) color table that endlessly repeats its
range.
-Z Creates a continuous CPT [Default is discontinuous, i.e., constant colors for each interval]. This
option has no effect when no -T is used, or when using -Tz_min/z_max; in the first case the input
CPT remains untouched, in the second case it is only scaled to match the range z_min/z_max.
-bi[ncols][t] (more …)
Select native binary input. [Default is the required number of columns given the chosen settings].
-dinodata (more …)
Replace input columns that equal nodata with NaN.
-icols[+l][+sscale][+ooffset][,…] (more …)
Select input columns and transformations (0 is first column).
-^ or just -
Print a short message about the syntax of the command, then exits (NOTE: on Windows just use -).
-+ 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 all options, then exits.
NOTES ON TRANSPARENCY
The PostScript language originally had no accommodation for transparency. However, Adobe added an
extension that allows developers to encode some forms of transparency using the PostScript language model
but it is only realized when converting the PostScript to PDF (and via PDF to any raster image format).
GMT uses this model but there are some limitations: Transparency can only be controlled on a per-object
or per-layer basis. This means that a color specifications (such as those in CPTs of given via
command-line options) only apply to vector graphic items (i.e., text, lines, polygon fills) or to an
entire layer (which could include items such as PostScript images). This limitation rules out any
mechanism of controlling transparency in such images on a pixel level.
COLOR HINGES
Some of the GMT master dynamic CPTs are actually two separate CPTs meeting at a hinge. Usually, colors
may change dramatically across the hinge, which is used to separate two different domains (e.g., land and
ocean across the shoreline, for instance). CPTs with a hinge will have their two parts stretched to the
required range separately, i.e., the bottom part up to the hinge will be stretched independently of the
part from the hinge to the top, according to the prescribed new range. If the selected range does not
include the hinge then no such partitioning takes place.
COLOR ALIASING
For best result when -T -Z is used we recommend you do no append a specific z_inc. This way the original
CPT is used exactly as is but the z boundaries are adjusted to match the stated limits. Otherwise you
may, depending on the nature of the input CPT, miss aspects of the color changes by aliasing the signal.
EXAMPLES
To make a CPT 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 from z = -2 to 6 using the continuous default rainbow of colors:
gmt makecpt -T-2/6 -Z > rainbow.cpt
To use the GEBCO look-alike CPT with its default range for bathymetry, run
gmt makecpt -Cgebco > my_gebco.cpt
or simply use -Cgebco directly in the application that needs the color table. 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
To use the gebco color table but reverse the z-values so it can be used for positive depth values, try
gmt makecpt -Cgebco -Iz > my_positive_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
To make a custom discrete color table for depth of seismicity, using red color for hypocenters between 0
and 100 km, green for 100-300 km, and blue for deep (300-1000 km) earthquakes, use
gmt makecpt -Cred,green,blue -T0,80,300,1000 -N > seis.cpt
To make a continuous CPT from white to blue as z goes from 3 to 10, try
gmt makecpt -Cwhite,blue -T3,10 -Z > cold.cpt
To make a wrapped (cyclic) CPT from the jet table over the interval 0 to 500, i.e., the color will be
wrapped every 500 z-units so that we always get a color regardless of the z value, try
gmt makecpt -Cjet -T0/500 -Ww > wrapped.cpt
BUGS
Since makecpt will also interpolate from any existing CPT you may have in your directory, you should not
use one of the listed cpt names as an output filename; hence the my_gebco.cpt in the example. If you do
create a CPT of such a name, e.g., rainbow.cpt, then makecpt will read that file first and not look for
the master CPT in the shared GMT directory.
SEE ALSO
gmt, grd2cpt
COPYRIGHT
2018, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe