Provided by: gmt-common_5.4.5+dfsg-2_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
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe