[GRASS5] Raster Color Tables

[Markus Neteler]

Hi Frank,

On Wed, Mar 21, 2001 at 09:08:53AM -0500, Frank Warmerdam wrote:
> Folks, 
> 
> Eric Miller has reported problems viewing greyscale rasters imported with
> r.in.gdal because the viewer is applying it's own rainbow color table in the
> absence of a color table being associated with the raster layer. 
The same happens with r.in.ascii and other import modules (where it usually
doesn't matter).

> My assumption in the past has been that raster layers without a colortable
> would be interpreted as greyscale, but now I guess that is not the case.  I 
> don't actually use the GRASS display subsystem so I wasn't aware of this issue.
> 
> So my question is, what are raster importers expected to do for greyscale
> images?  My current impressions is that I should change r.in.gdal to 
> create a 0-255 greyscale colormap for eight greyscale data, and use
> G_make_grey_scale_colors() for > 8bit data.  Is that right?  If so, I will
> update r.in.gdal in CVS, assuming this isn't too intrusive a change at this
> late date in the release cycle. 

I agree (as far as I understand the GRASS color model) that writing such a
color table is a good idea in case the import image is of grey scale type.

Regards

 Markus

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