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xycpt - Man Page

generate GMT colour palette table (cpt) files from column data.


xycpt [-b rgb] [-d] [-f rgb] [-h] [-n rgb] [-o file] [-r registration] [-u] [-v] [-V] [file]


The xycpt program generates discrete or continuous cpt files from simple input describing sample values of the colour (or greyscale) range. The input consists of 1–4 columns. For 2 and 4 columns, the first column is interpreted as a (double) z value, for 1 and 3 the z value is taken implicitly. For 1 and 2 columns the final column will be taken as a greyscale value. For 3 and 4, the last 3 columns are taken as RGB values.

The program will read from stdin if a file is not specified as the final argument, and write to stdout if the -o option is not specified.


In the following, all rgb specifications should be of the form red/green/blue where the colour components are integers in the range 0 to 255.

-b,  --background rgb

Set the background colour of the output.

--backtrace-file path

Specify a file to which to write a formatted backtrace. The file will only be created if there is a backtrace created, typically when an error occurs.

--backtrace-format format

Specify the format of the backtrace written to the files specified by --backtrace-file, one of plain, xml or json.

-d,  --discrete

Output a discrete cpt file, the default is continuous.

-f,  --foreground rgb

Set the foreground colour of the output.

-h,  --help

Brief help.

-n,  --nan rgb

Set the NaN (no data) colour of the output.

-o,  --output file

Write the output to file, rather than stdout.

-r,  --registration string

For discrete (using the -d option) conversion, specifies upper, middle or lower registration of the data value. For the upper and lower types the final (respectively the first) colour is omitted from the output; only the z value is used. For middle registration all the colours appear in the output.

-u,  --unit

Colour values are specified as floating point numbers in the range 0–1 rather than as integers in the range 0–255.

-v,  --verbose

Verbose operation.

-V,  --version

Version information.


J.J. Green

See Also



6 September 2023 cptutils 1.77 User commands