Sean,
thanks for the report. Support for GMT .cpt files dates back to 2010 and
hasn't evolved much since. So I assume GMT .cpt format might have
changed a bit since then. I've submitted a fix in
https://github.com/OSGeo/gdal/pull/14595 to support new files. In the
mean time you can manually adjust your .cpt file to please current
released GDAL versions by:
- replacing slashed with space
- and removing the trailing " L"
Even
Le 17/05/2026 à 22:24, Sean King via gdal-dev a écrit :
Hi folks,
I'm using GMT version 6.6.0 and GDAL version 3.12.4. I have
several CPT files that I generated in GMT using the makecpt command,
such as:
*/gmt makecpt -T-120/120/10 -I -Crainbow -Z -Fr/*
which generates the attached file. Then, I am trying to apply that
color palette to a TIFF file using 'gdal raster color'. The
documentation <https://gdal.org/en/stable/programs/gdaldem.html>
states that
*/GMT .cpt palette files are also supported (COLOR_MODEL = RGB only)./*
however, I continually get the error of
*/ERROR 1: No color association found in test.cpt/*
*/
/*
When I dug into the GDAL source code for the GMT CPT parser here
<https://github.com/OSGeo/gdal/blob/b3f839f2515b023e4a7cf099b7ce1626ccb24eac/gcore/gdalcolortable.cpp#L744>,
it really does not seem to match up with the current implementation of
GMT CPT files, even though the GDAL feature was added in the latest
release. For instance, it uses space, comma, tab, and colon as
delimiters, but no matter what flags I use for my GMT CPT generation,
I get a backslash as the delimiter, as seen in the attached file.
There are other inconsistencies as well.
Am I missing something? I'm somewhat new to GDAL and GMT, so I'd
appreciate any advice. Also, if this feature really to read GMT CPT
files is not adequate, is there a better way to approach this? I
essentially want to colorize a .grd file using gdal, so that I can
then generate map tiles with it. I have the rest of the pipeline
figured out, but I'm having issues with the color mapping. I wrote my
own converter from GMT CPT to GDAL color file, but it's a bit
buggy/hacky. I'm wondering if there is a more 'official' way to do this.
Thanks!
Sean
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