[GRASSLIST:3373] PNG driver 24 bit

HI,

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?

Ulrich

--
__________________________________________________

Ulrich Leopold MSc.

Computational Bio- and Physical Geography (CBPG)
Institute for Biodiversity and Ecosystem Dynamics (IBED)
Faculty of Science
University of Amsterdam
Nieuwe Achtergracht 166
NL-1018WV Amsterdam

Room: B2.52
Phone: +31 20 525 7456 (7451 Secretary)
Fax: +31 20 525 7431
Mobile: +31 64 220 3028
Email: uleopold@science.uva.nl
URL: www.science.uva.nl/ibed/cbpg

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:

  PNG: GRASS_TRUECOLOR status: TRUE

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
  GRASS_TRUECOLOR
  PNG: GRASS_TRUECOLOR status: TRUE

--
Glynn Clements <glynn.clements@virgin.net>