Colour problems on Linux - solved

[Rodrigo Caballero Augi <rca@xxxxxxxxxxxxx>]

The Problem:

>Hello,
>I've just installed Ferret v4.45 on a P6 with Red Hat Linux 4.2 (the
>kernel is v. 2.0.30). Everything works fine, except that the colours are
>all wrong: plot borders are red, the background is blue, and the shade or
>fill commands produce apparently arbitrary colours. Using GO white.jnl
>fixes the problem for line plots, but not for fill and shade. 
>The problems do not occur when logging in from a different computer (and
>hence using a different X server). However, all other X applications work
>fine on the local X server. 
>I very much appreciate any help.
>Thanks,
>Rodrigo

The Suggestions:

>Hi Rodrigo,
>I experienced the same problem on my pc running Red Hat 4.0, 
>but I can't tell you much about it.
>Just, that's related to whether you use pseudo or true colour. I believe,
>if you use pseudocolour it should work.... But since I actually I don't
>know anything about the pseudo or true colour stuff (what's the
>difference,which hard/software uses what, how do I change the setting....) I can't 
>tell you much more. I think I got it working on my machine with 256 true 
>colour - it won't work with more colours in true colour mode - I think.
>If you find out more about this stuff - I'd be most interested to hear...
>Sorry, but that's all I can say,
>good luck,
>Joerg
>--
>Jvrg Kaduk                                phone:  +1 (650) 325 1521 ext 416
>Carnegie Institution of Washington        fax:    +1 (650) 325 6857
>Department of Plant Biology
>260 Panama Street                         
>Stanford, CA 94305                        e-mail:joerg@jasper.stanford.edu

Well, you're right. It turns out Ferret will only work properly with 8bpp
PseudoColor. I happen to have a graphics card capable of 16bpp, and my X
server was configured to use 16bpp TrueColor, so it didn't work (looking
at man pages I've figured that "bpp" stands for "bytes per pixel"; with
8bpp you get 256 "true" colors (don't ask me why), but if you use pseudo
color then the server somehow pretends that it has more than 256, and
pictures look almost as nice as if you had 16bpp). Anyhow, in practice,
what you need is to have the folllowing lines in the Subsection "Display"
part of the XF86Config file:

Depth  8                # this sets 8bpp
Visual "PseudoColor"    # this is actually not essential since it's the
			# default with 8bpp


>Hello,
>Do you use the same window-manager on all systems ?  fvmw95 which is
>standard under Linux, uses a large fraction of the color table and does
>not leave enough for ferret. 
>Try twm or fvwm2 as a window managers. For me that fvwm2 works fine. I do
>not think that ferret has the option for creating it's own color table.
>It could be suggested to add this option. 
>Best regards and good luck
>                Jan
>
>Jan Polcher                                           TEL: -33-1-44277352
>Laboratoire de Mitiorologie Dynamique du CNRS         FAX: -33-1-44276272
>Tour 25, 5eme itage,  BP 99,     4 pl. Jussieu,      75252 PARIS cedex 05
>http://www.lmd.jussieu.fr/~polcher/            Jan.Polcher@lmd.jussieu.fr

With the adjustment above, Ferret is working fine with all the window
managers I tried (fvmw95, olvwm, fvwm2).


Thanks guys
Rodrigo


---

 Rodrigo Caballero Augi |Geophysics Department    |phone: +45 35 32 05 64
		        |NBIfAFG		  |fax:       35 36 53 57
 		        |University of Copenhagen |home:      31 23 05 80
		        |Juliane Maries Vej 30    |e-mail:  rca@gfy.ku.dk
		        |DK-2100 Copenhagen O     |http://www.gfy.ku.dk/~rca
			|Denmark