Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!prlhp1.UUCP!davidw
From: davidw@prlhp1.UUCP (David Walker)
Newsgroups: comp.windows.news
Subject: Playing with the colormaps
Message-ID: <3311.8905170713@prsun5f.prl.philips.co.uk>
Date: 17 May 89 20:20:22 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 19

>
>I have some 8-bit color bitmaps I would like to display under NeWS
>(via the readcanvas routine). It appears, however, that the NeWS
>colormap is static and that readcanvas just selects the closest
>color.
>

  We have the same problem displaying `real world' images on our sun3/60.
We gave up on trying to manipulate the colour map in NeWS and went for our
own picture coding software. I grabbed the NeWS clut from a header of a 
NeWS clut image and wroye my own software which approximated the pixel values
in my pictures to those available in NeWS. This is essentially what NeWS does
but in a simple way. My program uses the simplified Floyd-Steinberg algorithm
which essentially passes colour approximation errors to adjacent pixels on
the right, bottom, and bottom right of the pixel in question. This method 
gives a remarkable improvement in image quality.

  david walker
davidw@prl.philips.co.uk