Re: Linking to style sheets

lilley (
Fri, 7 Jul 1995 13:18:08 +0100 (BST)

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
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