cpt-city

GMT colour palette tables

• The format is described in the GMT Technical Reference and Cookbook. The standard palettes are shown in an Appendix of the same document.
• Manual page for the GMT programs makecpt and grd2cpt.
• The cptutils package provides some extra tools for manipulating cpt files.
• MapAbility's CPT Designer is a Windows GUI application for the creation and editing of cpt files (commercial with free trial period).

CSS3 gradients

• The W3C has recently defined a gradient format for the latest revision of the cascading style sheet standard.
• The standard is largely based on mozilla's version of CSS gradients, their documentation can be found here.

GIMP gradients

• The GIMP is an open-source drawing application with a fine gradient editor and a selection of built-in gradients, also available here.
• The gradient format is discussed in this thread on the gimp-developer mailing list.
• Rob Antonishen has written a GIMP plugin which creates a gradient by sampling along a path.

Gnuplot palettes

• Gnuplot is a portable command-line driven graphing utility under active development since 1986.
• Gnuplot uses colour palettes specified by formulae or data-files in a number of colour-spaces, using the “set palette” command. See, for example, the pm3d, pm3dcolors and hidden2 demos.
• The gpf files on cpt-city are Gnuplot palette files in the RGB colour-space. See “help set palette file” in the Gnuplot shell for more information.

SAO colour maps

• External SAO colour maps can be used in DS9 either from the command line (see the -cmap option) or from the colormap parameters dialogue in the color menu in the GUI. In the latest beta version of DS9 one can browse cpt-city directly from colormap parameters → file → download colormap. Clicking on an "sao" link loads the map directly into the program.
• The CHiPS plotting system for the Chandra X-ray observatory also uses SAO format colour maps.
• The SAO format is simple ASCII with independent RGB channels of linear splines. More details on the format can be found on the SAOimage site.

SVG gradients

• The W3C has defined an XML-based gradient format as a part the SVG vector graphics format.
• The open clipart library contains a number of SVG gradients (translated here).

POV-Ray colour maps

• The free ray-tracing program POV-Ray supports colour-maps as part of its complex pigment type.
• The online documentation for version 3.6.1 describes the syntax and has several coding examples.

R

• R is an open-source statistics package implementing advanced statistical algorithms and with a powerful and intutive graphics capability.
• Sergio Ibarra-Espinosa of the Universidade de São Paulo maintains an R package making the gradients of cpt-city available in R graphics scripts.
• Development of the package takes place in the GitHub repository, which also contains documentation and examples of usage.

Cinema 4D

• The gradients from cpt-city can be imported into the Cinema 4D package using the gimp-gradient plugin by Ian Gorse.

GRASS

• Users of the GRASS GIS system can import the cpt files on cpt-city using the r.cpt2grass script from the GRASS Add-ons collection.
• Information on the use of colour maps in GRASS can found on Hamish Bowman's Peripheral Visionary pages.

IDL

• Michael Galloy has written an IDL routine to read a cpt file and return it as a 256 by 3 color table array.

Matlab, Octave

• One can use cpt files in the Matlab and Octave linear algebra packages with the colormap_cpt m-file by Thijs Damsma, part of the OpenEarthTools collection.
• The MathWorks hosts a CPT for Matlab package which allows cpt files to be loaded as Matlab colour-maps.

Python

• GMT cpt files can be loaded dynamically into Python/matplotlib using James Boyle's gmtColormap.py script which is archived in the SciPy cookbook.
• Incomplete but possibly interesting: Robert Smallshire's pycpt aims to provide comprehensive cpt support for Python.
• See also Jonas' package of the same name.

Medcon

• The open-source medical image viewer medcon uses a simple 256 level lookup table (LUT) for its colour gradients.
• The GIMP gradients on cpt-city can be converted to the LUT format with the gimplut program, part of the cptutils package

Paint Shop Pro

• Paint Shop Pro uses version 3 of the grd format for its gradients. Typically the files have the extensions .PspGradient or .jgd.
• The format is undocumented but rather simple: a technical description can be found here.

Photoshop

• Photoshop uses various versions of the of the grd format, and can read the version 3 files on cpt-city. This amusing thread on Usenet discusses the later versions.
• Matt Schraeder describes a method for converting the complete set of grd version 3 gradients on cpt-city to a single Photoshop gradient in his frozen solid blog.

See also the general links page.