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Re: [CSS4 color][CSS4 transition] color pre-multiplied vs non pre-multiplied was (Re: [CSSWG] Minutes TPAC Tue 2012-10-30 AM I: Abstract Directions, Transforms, Transitions)

From: Alan Gresley <alan@css-class.com>
Date: Tue, 05 Feb 2013 15:03:59 +1100
Message-ID: <511084AF.5080003@css-class.com>
To: Brad Kemper <brad.kemper@gmail.com>
CC: Simon Fraser <smfr@me.com>, Rik Cabanier <cabanier@gmail.com>, fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>
On 5/02/2013 2:53 PM, Alan Gresley wrote:

> Brad. I'm just wondering what type of background you plan to use under
> any gradient with alpha transparency?
> A pre-multiplied gradient of yellow to transparent to blue is identical
> to a non pre-multiplied gradient of yellow to transparent-white to blue
> when composite on a white background. There is _no need_ for an extra
> color stop.

Wrong and correction. A pre-multiplied gradient of yellow to transparent 
to blue compiste of a whitye background is identical to a gradient of 
yellow to white to blue (fully opaque).

What do you want to achieve with a gradient that has alpha transparency 
and have you tested any of this by observing the difference between 
pre-multiplied colorspace and non pre-multiplied colorspace?

Alan Gresley
Received on Tuesday, 5 February 2013 04:04:28 UTC

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