[Mapserver-users] reducing RGB maps to 8bit

[Ken Boss]

Jan--

Hope I'm not catching you after a full week's worth of coding on this;
didn't see your message until a couple days ago, and then I needed to
confirm with the software vendor that this was in fact possible.

Anyway, Image Alchemy from Handmade Software, Inc., has this
functionality built in  (-L option on the command line).  You run the
software once with your list of images as input, and it generates a file
containing the optimized palette for those images.  Then you batch up a
process to transform them all to 8bit, using the palette you generated
in the first step.

Image Alchemy is a relatively inexpensive commercial software product
that runs on any OS you're likely to be using; I've been using it for
years on both Solaris and Windows and have been very happy with it.  You
can learn more at www.handmadesw.com.

Note that I am not affiliated with Handmade Software in any way, other
than being a satisfied customer.

--Ken

>>> Jan Hartmann <jhart at frw.uva.nl> 3/23/2004 3:53:30 AM >>>
Hi,

Not a specific MapServer question, but I guess there are people on this

list who know something about this. I have about 600 historical 
cadastral maps dating from about 1830. They have been scanned as 24bits

jpg files, and each map is about 4000*4000 pixels. To display them 
efficiently with MapServer I need to transform them to 8bit, all in the

same palette. Colors on the different maps don't match exactly, due to

two centuries of wear and tear The question is: does anyone know a way

to compute some sort of optimal colormap for this amount of data, 
something like "imagemagick -display" or the gdal-utility "rgb2pct.py",

  not for a single file, but for a large set of images. There is some 
literature about it, e.g. "comp.graphics.algorithms 3.02"  and
"graphics 
gems", but before I start programming myself, perhaps someone knows an

easier way.

Thanks,

Jan
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