Re: HTML 3.2 PR color value syntax

David Perrell (davidp@earthlink.net)
Wed, 13 Nov 1996 13:00:49 -0800


Message-Id: <199611132102.NAA11140@armenia.it.earthlink.net>
From: "David Perrell" <davidp@earthlink.net>
To: <www-html@w3.org>, "Chris Lilley" <chris@w3.org>,
Subject: Re: HTML 3.2 PR color value syntax
Date: Wed, 13 Nov 1996 13:00:49 -0800

Chris Lilley wrote:
> I seem to recall that it is explicitly mentioned and also explicitly
> illustrated. The rule is to extend by replication. So your example of

> #f07becomes #ff0077 or fff000777 or ffff00007777. This rule ensures 
> that it is always possible to get zero intensity and full intensity
> and that the intervening values are evenly spaced (in RGB).

Three- and six-digit representations are illustrated, and extension
from three to 6 digits is explicitly mentioned:

"Note that the three-digit RGB notation (#rgb) is converted into
six-digit form (#rrggbb) by replicating digits, not by adding zeros.
For example, #fb0 expands to #ffbb00."

Perhaps the above paragraph should be expanded to read:

"The hexadecimal RGB (#rgb) notation can be any multiple of three
digits. In the case where an output device has greater color resolution
than the RGB values, the values are expanded by replicating digits. For
example, the 12-bit value #fb0 is expanded to #ffbb00 for 24-bit
output. In the case where an output device has less color resolution
than the RGB values, the insignificant digits are ignored. For example,
the 48-bit color value #ff12bb120012 is reduced to #ffbb00 for 24-bit
output."

--------
There was a suggestion a while ago to expand the CSS color triplet
notation to include alpha channel in the color spec, as in

           rgba(255, 127, 0, 63)

This seems like a great idea. Why wait for CSS2?

In this case it should be possible to mix value types in a triplet or
quadlet(?) so that the above could be:

           rgba(255, 127, 0, 25%)

David Perrell