[GRASSLIST:1415] Re: r.patch geotiff-mosaic wrong color problem

[Juergen Ambrosy]

Thanks for replying, Mr.Greenwood, Mr.Warmerdam,

Mr. Greenwood, could you explain which steps are necessary to preprocess the 
8bit-tiff images with Gimp, so that all use the same color palette?
If possible I want to avoid using 24bit geotiff, I think gdal can't even 
import 24bit geotiff, only 8bit. So I need r.in.tiff to import and 
georeference it afterward which I want to avoid, too.

> An 8bit tiff uses a color palette. The value of any given pixel is used to
> lookup the red,green,blue value in a table. The table is the palette, and
> is a part of the tif file. It is likely that each of tiff's has a different
> palette. The color table for each image is in the colr directory of your
> location. They are just ASCII files.
>
> You can preprocess each image with Gimp or Photoshop so that they all have
> the same color palette before you import them into GRASS, or you can
> convert them to 24bit tiffs before importing. In a 24bit tiff each pixel
> has 3 bytes, one each for red, green, and blue, so no color palette is
> used.
>
> Rich
>
>
>
> Richard W. Greenwood, PLS
> Greenwood Mapping, Inc.
> Rich <at> GreenwoodMap <dot> com
> (307) 733-0203
> http://www.GreenwoodMap.com

-- 
Juergen Ambrosy

juergen.ambrosy at ewetel.net