d.rgb d.his

[Dave Gerdes]

> Date: Tue, 14 Apr 1992 16:57:17 -0500
> From: Jim Westervelt <westerve at marla.urban.uiuc.edu>
> Message-Id: <199204142157.AA04511 at marla.urban.uiuc.edu>
> Sender: lists-owner at amber.cecer.army.mil
> Reply-To: grassu-list at amber.cecer.army.mil
> Precedence: Bulk
> To: grassu-list at amber.cecer.army.mil
> Subject: d.rgb d.his
> 
> 
> Jinn-Guey Lay questions:
> 
> #I was trying to display an elevation map in color with a shadow 
> #releif map in grey tone. I have tried 'd.his' using elevation
> #as hue and shadow relief as intensity. It looks OK only if I stay
> #far enough; the display is somehow noisy with many pixels of
> #different colors scattering arround.
> 
>  This is probably the best that GRASS (and your display monitor) can do.
>  I suspect that the scattering of different colors would be corrected if
>  you put the monitor into "fixed" mode.  (d.colormode fixed)  If the
>  scattering you talk about is on the subtle side - colors just slightly off,
>  then your colormode is "fixed" and the d.his program is dithering the
>  available colors to get the best representation it can out of a 6x6x6
>  color table (RxGxB).   Basically you (and GRASS) are asking too much of
>  8 bit planes of graphics - you are experiencing the lure of 24 bit plane
>  devices.
> 

etc etc.


Try using 
    blend.sh elevation.file aspect.file 70

to create 3 band files (R,G,B)

(or I passed out a copy of intens.sh on this newsgroup a while back.  It 
will do an even better job)


Then if you have a Silicon Graphics workstation you can use the
Dtrue program to display the resultant composit in true 24 bit color.
If not, use i.median to combine the 3 files into one 8 bit color file.

i.median creates a file with a colortable of 256 colors.  This can be
displayed on any GRASS display, but it usually will look much better if
you can display it in float mode on a display which will support 256 colors.
You can acheive this in SUNVIEW by setting an environment variable before
starting the monitor.

    setenv GRASS_COLOR256
    d.mon sunview

I am not sure whether Xdriver supports this or not.

This should be part of the FAQ.

Oh, we don't have a FAQ.


  Dave Gerdes
  US Army Construction Engineering Research Lab
  Spatial Analysis & Systems Team
  dpgerdes at cerl.cecer.army.mil
  (217) 352-6511 x591