makecpt (1gmt)

makecpt [ -Ctable ] [ -I ] [ -Tz0/z1/dz | -Tztable] [ -V ] [ -Z ]

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.

-C

Selects the master color table table to use in the interpolation. Choose among the built-in tables (type makecpt to see the list) or give the name of an existing cptfile [Default gives a rainbow cpt file].

-I

Reverses the sense of color progression in the master cptfile.

-T

Defines the range of the new cptfile by giving the lowest and highest z-value and the interval. Alternatively, give the name of a ASCII file that has one z-value per record. If not given, the existing range in the master cptfile will be used intact.

-V

Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].

-Z

Creates a continuous cpt file [Default is discontinuous, i.e. constant colors for each interval].

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, try

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, try

makecpt -T-2/6/1 -Z > rainbow.cpt

To make a GEBCO look-alike cpt file for bathymetry, try

makecpt -Cgebco > my_gebco.cpt

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.

gmt(1gmt), grd2cpt(1gmt)