Supported formats
The gradients on cpt-city are usually available in each of the following file formats:
- Colour palette tables for use with the Generic Mapping Tools, GMT (cpt)
- Gradients for the GNU image manipulation program, GIMP (ggr)
- Version 3 of the grd format, which can be read by Paint Shop Pro (up to version X) and by Photoshop (grd)
- POV-Ray colour map headers (inc)
- Scalar vector graphics gradients (svg)
There are some gradients which have not (or cannot) be translated to some formats. The main restrictions are:
- GMT colour palettes (cpt) can have levels painted by a bitmap (hatchure) which cannot sensibly be converted to other formats
- GMT colour palette (cpt) and GIMP gradient (ggr) files support non-RGB colour models. These are not yet converted to the other formats.
- The cpt format does not have an alpha-channel (since transparency is not supported in PostScript, GMT's output format) so conversion to the cpt format is achieved by replacing the transparency by white, but this can lead to seemingly pointless cpt files
Some of the POV-Ray colour-map (inc) files available on cpt-city
contain more than 256 colours; the limit for current versions of the
POV-Ray software. If you want to use a larger palette then you'll
need to increase the value of MAX_BLEND_MAP_ENTRIES in
source/frame.h in the POV-Ray sources and recompile it.
Note that POV-Ray imposes
restrictions
on the distribution of modified sources.
Photoshop can only handle 56 levels in a version 3 grd file and will truncate larger files.
The grd and inc files which are too large for their programs have the links to the files greyed out: the files are there, but probably won't work.
Paint Shop Pro users may need to rename the grd files (with extension PspGradient) to have them recognised by the program. Or can import them.
Other gradient formats may be added at a later date, although only formats which are fully open (and reasonably documented) will be considered for inclusion.
Further information on gradients can be found on the links page.