| Re: Converting 24bit images to 8 bit [message #922] |
Mon, 15 March 1993 07:14 |
guy
Messages: 2
Registered: April 1993
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Junior Member |
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In article <1993Mar10.140851.9050@infodev.cam.ac.uk>, gdc11@cus.cam.ac.uk (G.D. Carver) writes:
>
> Can anyone help me out with a better algorithm to convert the 24bit images to
> 8bit? The obvious first step is to scan the red, green and blue images to
> actually see what colours are required. This will undoubtedly produce more than
> 256 colours and the not-so-obvious next step is how to reduce the no. of colours
> required.
>
> If anyone can help out with some algorithms or point me in the direction of
> some reference material I would be extremely grateful.
>
I had the same problem some time ago. IDL has a very nice routine COLOUR_QUAN which
does the 24bit to 8bit quantisation, with very nice results. I had my images processed
by a collegue using IDL. Other than this, there are a number of tools which can do
the job for you, including PPM, URT and Imagic. The comp.graphics faq gives references and
mentions a couple of papers you might want to try. This can be obtained from
(18.172.1.27) as pub/usenet/news.answers/graphics/faq.
You might also like to look at Graphics Gems I, II and III which contain papers about
color quantisation. The sources for these are available at princeton.edu (128.112.128.1) in pub/Graphics/GraphicsGems and many other sites.
If you implement anything in PV~Wave itself, please let me know, as it would save
transferring things between various file formats !
Guy
--
------------------------------------- Guy Brooker
Internet: guy@wm.estec.esa.nl European Space Research and
guy@estwm0.dnet.estec.esa.nl Technology Centre (ESTEC)
gbrooker@estec.esa.nl
Bitnet : gbrooker@estec SPAN : ESTERS::GUY
Phone : +31-1719-83611 Fax : +31-1719-85617
Mail : ESTEC JW/WMS, Keplerlaan 1, 2200AG NOORDWIJK, The Netherlands
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