[GRASSLIST:3375] Re: PNG driver 24 bit

Glynn Clements glynn.clements at virgin.net
Fri May 7 21:34:56 EDT 2004

Ulrich Leopold wrote:

> I do not manage to get true color support. I installed the png driver
> with 24 bit.
> But when I 'export GRASS_TRUECOLOR=TRUE' for the PNG monitor the map
> legend appears with steps in the color change. In the X-monitors it is
> shown correctly with a smooth change in colours.
> I guess this is because of non-true colours?
> gd-2 and libpng-1.2.5 are installed.
> Any ideas how I can achieve the true color support and a smooth gradient
> in the legend for the PNG monitor?

Does "d.mon start=PNG" print the message:


If it doesn't, then either the PNG driver was built without
true-colour support, or the GRASS_TRUECOLOR environment variable
hasn't been set correctly.

You can check whether the PNG driver was built with true-colour
support by running "strings" on it and checking for the existence of
the string GRASS_TRUECOLOR in the output, e.g.:

	$ strings /usr/local/grass5/driver/PNG | fgrep GRASS_TRUECOLOR

Glynn Clements <glynn.clements at virgin.net>

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