W3C home > Mailing lists > Public > www-style@w3.org > June 2011

(unknown charset) Re: [CSS3-color] [css3-images] [css3-transitions] transparent transitions

From: (unknown charset) L. David Baron <dbaron@dbaron.org>
Date: Mon, 27 Jun 2011 10:52:52 -0700
To: (unknown charset) fantasai <fantasai.lists@inkedblade.net>
Cc: (unknown charset) www-style@w3.org, Tantek Çelik <tantek@cs.stanford.edu>
Message-ID: <20110627175252.GA9945@pickering.dbaron.org>
On Monday 2011-06-27 13:46 -0400, fantasai wrote:
> On 01/12/2011 12:26 PM, Tab Atkins Jr. wrote:
> >
> >What you're seeing is the fact that transitions from opaque colors to
> >transparent in non-premultiplied space get darker as they progress.
> >Try doing a transition from opaque white to transparent over a white
> >background, and you'll see it very clearly - you'll get an image that
> >starts white, darkens to gray, and then lightens to white again.
> 
> Is there a way to avoid things like this? It seems to me that having
> 'transparent' mean 'transparent black' means you almost never get what
> you want, which is the opacity fading without the color itself changing.
> I think that's a common enough use case that it should be easy to do.

The way to avoid it is to transition in premultiplied space instead.
(Gecko does this for transitions, but not yet for gradients.)

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/
Received on Monday, 27 June 2011 17:53:22 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 17:20:41 GMT