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Re: Linking to style sheets

From: lilley <lilley@afs.mcc.ac.uk>
Date: Fri, 7 Jul 1995 13:18:08 +0100 (BST)
Message-Id: <10587.9507071218@afs.mcc.ac.uk>
To: mikebat@clark.net (Mike Batchelor)
Cc: www-style@www10.w3.org
Mike Batchelor said:

> I've noticed another quirk, which is not really a big deal, but quirky
> nonetheless.  For red, any value less than 9 is rendered black, for blue
> also, anything less than 9 is rendered black, and for green, anything less
> than 7 is rendered black.  So you can get a darker green than you can red
> or blue. :)   Maybe its just my display...

This is a consequence of the way Arena allocates colours on displays 
with inadequate colours (ie 8bit or less). It would appear (from using 
xcmap) that Arena allocates a 128 element colour rectangle: 4 red x 5 
green x 4 blue, plus a 14 element grey ramp (16 elements including black 
and white)

This is a good way to do it, because green contributes most to the 
luminance information and we are less tolerant of big steps in luminance 
than of big steps in chrominance.

I hope to analyse the perceptual spacing of different browsers colour 
allocation strategies, but this will take a bit of time.

I hope I need not add that pages should not assign colours based on this 
observed behaviour, but should specify the desired colours and let the 
browser worry about how to represent them.

Chris Lilley, Technical Author
|       Manchester and North HPC Training & Education Centre        |
| Computer Graphics Unit,             Email: Chris.Lilley@mcc.ac.uk |
| Manchester Computing Centre,        Voice: +44 161 275 6045       |
| Oxford Road, Manchester, UK.          Fax: +44 161 275 6040       |
| M13 9PL                            BioMOO: ChrisL                 |
|     URI: http://info.mcc.ac.uk/CGU/staff/lilley/lilley.html       | 
Received on Friday, 7 July 1995 08:18:40 GMT

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