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Re: [css-compositing] How do 'alpha-compositing' and 'blend-mode' interact?

From: Rik Cabanier <cabanier@gmail.com>
Date: Sat, 21 Jul 2012 23:40:12 -0700
Message-ID: <CAGN7qDBxSgTgTytGq=vXU9__-AKoyGhdyjZarO7AbHQZKfWu3A@mail.gmail.com>
To: Maciej Stachowiak <mjs@apple.com>
Cc: www-style list <www-style@w3.org>
On Sat, Jul 21, 2012 at 11:21 AM, Maciej Stachowiak <mjs@apple.com> wrote:

> How do 'alpha-compositing' and 'blend-mode' interact if you have set both?
> I was unable to determine this from the spec. Does it actually make sense
> to specify both to non-default values at the same time?

Yes, it does in certain use cases.
Say for instance, you have text that is blending with a video underneath,
but I also want the text to clip the video. (see for instance the Marvel
trailer : http://www.youtube.com/watch?v=aTDNosVEEyk)

> I was unable to understand what their relationship is supposed to be.
> Some other comments:
> - The property values for the 'alpha-compositing' operator are
> inconsistent with the values for HTML5 Canvas: <
> http://www.w3.org/TR/2dcontext/#dom-context-2d-globalcompositeoperation>.
> I suggest making them match if there is no compelling advantage to the new
> names, otherwise this will be needlessly confusing to authors.
> - Consider renaming 'alpha-compositing' to 'composite-operator' for
> similar reasons.
> Regards,
> Maciej
Received on Sunday, 22 July 2012 06:40:40 UTC

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