GRASS colors

[Bill Brown]

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> Dear Grass-users ,
> 
> The following question of mine is beyond GRASS works, but in future
> it need  GRASS works in various its application, in my opinion.
> 
> Q: In GRASS, just 0-255 integer rast-based color coding image is possible,
>    but how about dynamic range color/gray scale image with real number?
>    Is possible now in GRASS ?
>    If not, anyone know Unix-based gray scaling and image generation software
>    and its ftp site ?
>    Actually, at XV( ver 3.0), I handled gray image after assignment into 
>    proper integer number from real number, but some loss of original information...
> 
> Looking forward help...
> Thanks in advance.
>                                                            Kiwon
> 
> ps; I must express my thanks to M. Ameskamp, J. D. McCauley, and J. L. Aycrigg
>     for their advice about my previous question. Now no problem, work out.
>   
>   
> 

Using GRASS color files, you can specify values from 0-255 for EACH 
of the three (red,green,blue) color components, yielding something
like 16 million possible colors.  Of course, the problem comes in 
trying to display your map.  There are severe limitations with the
GRASS X-driver and with 256 color 8-bit monitors.  But even with
24-bit displays, the GRASS X-driver still limits you to something
like 216 colors.  (I understand that the tcl/tk viewer will let you
use all your available color depth).  But for now, if you have a
display device capable of more colors, you could use r.out.ppm to
convert the GRASS raster file into a 24-bit ppm image, then output
that.

And just a reminder that if you're running on an SGI with 24-bit
graphics, don't overlook the IRIS monitor driver, which will give
you 3840 colors.

-Bill