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Re: [CSS3-color] [css3-images] [css3-transitions] transparent transitions

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 28 Jun 2011 11:27:47 -0700
Message-ID: <BANLkTinhfXrTFMGatD1MEM9DSSo1dO_BnbCiCT4S4Y+Y6BpEiA@mail.gmail.com>
To: fantasai <fantasai.lists@inkedblade.net>
Cc: www-style@w3.org, Tantek Çelik <tantek@cs.stanford.edu>
On Mon, Jun 27, 2011 at 10:46 AM, fantasai
<fantasai.lists@inkedblade.net> 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.

dbaron's got it - Image Values requires gradients to transition in
premultiplied space for precisely this reason.  Premultiplied
transitions are identical to non-premultiplied when you hold either
the alpha or the color steady, and they're generally more attractive
when both the color and alpha change at the same time.

~TJ
Received on Tuesday, 28 June 2011 18:28:34 GMT

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