[Mapserver-users] preprocessing 24bit Rasterdata

[Frank Warmerdam]

Christina Biakowski (CCGIS) wrote:
> Hello,
> since I am still using Mapserver 3.6, I have to convert my rasterdata (24bit
> orthophotos, TIFF) into 8bit.
> Does any of the GDAL-utilities supply this convert-function? I am not very
> familiar with image-formats and properties and searching the gdal-site and
> the mailing-archive did not help to answer my question.
> Or which other tool I could use alternatively to convert my images? (in a
> batch-process, because I have quite a lot images to convert. The image
> processing program I am using does not support the conversion in a batch.)
> Thanks a lot!
> Regards,
> Christina


Christina,

GDAL has a Python script utility called rgb2pct.py that can be used for
compressing a 24bit image to an 8bit pseudo-colored image.  It uses "optimal"
colortable selection, and dithering to give the best representation I know
how.

As Vincent mentioned, imagemagick is also very good and is even more flexible
in options.  The advantage of GDALs rgb2pct.py is that is preserves any
georeferencing.

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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