[GRASS-user] exporting single banded float raster to true color geotiff (i.e. 3 Byte bands with color interpretation)

[Markus Metz]

On Mon, Sep 19, 2011 at 11:15 AM, G. Allegri <giohappy at gmail.com> wrote:
> Thanks Hamish, r.out.tiff did the work. I already had tried it but I failed
> because I dind't set the region correctly.
> Anyway, setting the -t flag writes the TFW but doesn't make it a *true*
> GTiff, because r.out.tiff writes a Baseline tiff, without the GTiff tags.
> But that isn't a problem of course, I can produce a GTiff with another step
> (eg gdal tools).

You can export a true GTiff with color as cell values instead of
original cell values with

# extract RGB values
r.mapcalc "mymap.r = r#mymap; mymap.g = g#mymap; mymap.b = b#mymap"

# create RGB group
i.group group=mymap.rgb in=mymap.r,mymap.g,mymap.b

# export RGB group
r.out.gdal in=mymap.rgb out=mymap.tif -c

The -c flag to skip export of the colortable because the raster values
themselves hold the color info.

Markus M

> giovanni
>
> 2011/9/17 Hamish <hamish_b at yahoo.com>
>>
>> Giovanni wrote:
>> > The question is the object :)I have a Float raster which GRASS
>> > displays with a certain color table (I haven't set it...
>> > PS: what table is used by default?). What's the most effective
>> > way to export the raster into a true color Geotiff (as a 3 Byte
>> > bands with color interpretation) using a certain color table?
>>
>> I believe that r.out.tiff will export using colors, not data.
>> Add the -t flag to get a world file & so make it a geotiff.
>>
>> In GRASS 6.4 the d.out.file module is another option, set the
>> size= parameter to the number of rows and columns, and select
>> format=geotiff.
>>
>> The default color table is "rainbow", see the r.colors help page
>> for details.
>>
>>
>> Hamish
>
>
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