- From: lilley <lilley@afs.mcc.ac.uk>
- Date: Fri, 7 Jul 1995 13:18:08 +0100 (BST)
- 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 UTC