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Re: [css-color] Have you considered standardizing a rgba(#RRGGBB, <alpha-value>) notation?

From: Simon Sapin <simon.sapin@exyr.org>
Date: Thu, 09 May 2013 15:06:08 +0200
Message-ID: <518B9F40.5030602@exyr.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Sebastian Zartner <sebastianzartner@gmail.com>, Jake Archibald <jaffathecake@gmail.com>, Lea Verou <lea@w3.org>, Šime Vidas <sime.vidas@gmail.com>, www-style list <www-style@w3.org>
Le 08/05/2013 17:17, Tab Atkins Jr. a écrit :
> On Wed, May 8, 2013 at 3:52 AM, Sebastian Zartner
> <sebastianzartner@gmail.com> wrote:
>> Since different kinds of color values are involved in these examples, using
>> rgba() doesn't make sense here. alpha() seems more logical to me.
> Agreed.  I'm thinking maybe a pair of functions for each component,
> set-*() and adjust-*(), for either overriding the given channel or
> adjusting it up or down.  Hmm, though, there's argument for both
> adjusting by a set amount, and by a percentage amount, at least for
> some channels.  I'll look into what the preprocessors do, precisely.

I don’t have much practice using such functions, but setting/adjusting 
individual color channels seems more useful in HSL space than RGB.

As to alpha, I think that multiplying is the obvious thing to do. For 
example, the used alpha here would be 0.3:

.foo {
   var-bar: rgba(255, 0, 128, 0.6);
   background: alpha(var(bar), 0.5);

This simplifies to "set" if the first argument’s alpha channel is 1. I’m 
not sure if the second argument or the result should be clamped to 0..1.

Simon Sapin
Received on Thursday, 9 May 2013 13:06:31 UTC

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