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Re: [css3-color] #rrggbbaa annotation

From: Alan Gresley <alan@css-class.com>
Date: Sat, 15 May 2010 14:37:56 +1000
Message-ID: <4BEE2524.20006@css-class.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Simon Fraser <smfr@me.com>, Patrick Garies <pgaries@fastmail.us>, Brad Kemper <brad.kemper@gmail.com>, Alberto Lepe <dev@alepe.com>, www-style list <www-style@w3.org>
Tab Atkins Jr. wrote:
> I submitted my very first patch to Webkit today, to add this syntax:
> https://bugs.webkit.org/show_bug.cgi?id=39140 .
> I'm still ambivalent about adding this to Level 3, but given the
> triviality of the patch, and the presumed triviality of similar
> changes to the other browsers, I highly doubt it would slow down the
> progression of Level 3.  Lachy has expressed a desire to get Opera to
> support it, and Sylvain has said that he'll at least support a
> proposal.
> The spec change is similarly trivial.  Replace the second paragraph
> under "RGBA Color Values", which starts with "Unlike RGB values...",
> with "The format of an RGBA value in hexadecimal notation is a ‘#’
> immediately followed by either four or eight hexadecimal characters.
> The four-digit RGB notation (#rgba) is converted into eight-digit form
> (#rrggbbaa) by replicating digits, not by adding zeros.  The last two
> digits are divided by 256 to form an <alphavalue>."  Then add the
> obvious examples to the two example sections.
> (I actually need to go check and see what exactly we do with the
> mapping.  0x80 maps to .5, but 0xFF maps to 1.0.  Something seems
> slightly amiss here...)
> ~TJ

Nothing is amiss, that is hexadecimals notation. 16 values are 
possible from 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E and F. We have two sets of 
hexadecimals which gives us 256 values (16 x 16 = 256).

0x00 maps to 0
0x80 maps to 0.5
0xFF maps to 1.0

Alan http://css-class.com/

Armies Cannot Stop An Idea Whose Time Has Come. - Victor Hugo
Received on Saturday, 15 May 2010 04:45:10 UTC

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