MAKECPT

makecpt − Make GMT color palette tables

makecpt [ −Ctable ] [ −D ] [ −I ] [ −N ] [ −Q[i|o] ] [ −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].

−D

Select the color values for lowest and highest z-values in the output cpt file as the back- and foreground values that will be written to the cpt file [Default uses the GMT default values, normally black and white].

−I

Reverses the sense of color progression in the master cptfile.

−N

Do Not write out the background, foreground, and NaN-color fields [Default will write the parameters COLOR_BACKGROUND, COLOR_FOREGROUND, and COLOR_NAN in your .gmtdefaults4 file.

−Q

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.

−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:

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:

makecpt −T-2/6/1 −Z > rainbow.cpt

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

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(l), grd2cpt(l)