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Re: [CSS3-images] premultiplied alpha (was rotate(<angle>[, <translation-value>, <translation-value>]))

From: Rik Cabanier <cabanier@gmail.com>
Date: Tue, 21 Feb 2012 12:21:39 -0800
Message-ID: <CAGN7qDBbiQ0k4F_wG6LXX_ay4dL58qHE7-t36aOO+Mz4Y7S0nA@mail.gmail.com>
To: Brian Manthos <brianman@microsoft.com>
Cc: "L. David Baron" <dbaron@dbaron.org>, "Tab Atkins Jr." <jackalmage@gmail.com>, www-style list <www-style@w3.org>
On Tue, Feb 21, 2012 at 11:56 AM, Brian Manthos <brianman@microsoft.com>wrote:

> Rik:
> > Well, you *could* special case 'transparent' to say use a transparent
> version
> > of the previous or next color stop which is really what the author means.
> This was also discussed in depth and had concerns.
> Some of the concerns:
> - "special case of 'transparent'": animations and transitions become
> incredibly complex with no "correct" answer in at least some situations
> - "use the transparent version of the previous or next stop": well which
> one?  Or is it both depending on situation?

it would be both (unless it's the first or last)

- "what the author means": any spec that implies the editor knows what the
> author means is usually wrong in its generic boldness

Well, in the case of going from rgb(255, 0, 0) to rgb(0, 255, 0, 0), I'm
pretty sure the author didn't mean that you should ignore the red value...

> +1 @ my posts about improving "memory" coming out of this forum.
> L. David Baron:
> > Choosing premultiplied means optimizing for the normal case rather
> > than the odd feature of transition to transparent + color.
> Rik:
> > I don't think going from red to transparent yellow is an odd case at
> all. It
> > gives you a similar effect to InDesign's gradient feather.
> I think it's a reasonable scenario but also reasonable for CSS to draw the
> line somewhere regarding what to support directly.
> The PROs and CONs of { (a) premultiplied, (b) not premultiplied, and (c)
> both available } were discussed in depth multiple times and the conclusion
> (to my recollection CSSWG resolution) was to go with (a) for CSS3.  There
> was some gnashing of teeth in response, but mostly localized to a few
> voices.
If this issue was brought up at the WG, discussed and consensus was
reached, there's no need for me to rehash it.

Thanks Brian!
Received on Tuesday, 21 February 2012 20:22:15 UTC

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