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Re: [filter-effects] feBlend filter

From: Rik Cabanier <cabanier@gmail.com>
Date: Thu, 30 May 2013 08:22:59 -0700
Message-ID: <CAGN7qDCSq8XLdbnej9-oOWTo+mcikfWHLe0yg9EPmGQ+z-A_gg@mail.gmail.com>
To: Tavmjong Bah <tavmjong@free.fr>
Cc: public-fx@w3.org, www-svg <www-svg@w3.org>
Hi Tav,

On Thu, May 30, 2013 at 1:49 AM, Tavmjong Bah <tavmjong@free.fr> wrote:

> On Wed, 2013-05-29 at 13:52 -0700, Rik Cabanier wrote:
> There is a perhaps a more obvious example at:
> http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Filters-Compositing.html

yes, this is the "double counting background" issue that is mentioned on
that page.

> I don't know where the comment in the text about this problem being
> fixed in SVG 1.2 came from. I can't find anything in the that spec about
> it.

Maybe they were thinking of the SVG compositing spec?

> A cleaned up SVG file of this example is attached. The example renders
> as expected in Opera, Batik, srvg, and Inkscape, but not in Firefox or
> Chrome.

Your example fixes the issue with alpha in the backdrop by matting with
However. as I showed in my example yesterday, the problem also happens when
you have alpha in the source and I haven't looked into how that can be
fixed with the current spec.

> I think that this is an important enough flaw in SVG 1.1 that breaking
> backwards compatibility may be warranted.

Maybe we can add special handling when you use background image in feBlend?
It's ugly but wouldn't break site that use feBlend to blend with
intermediate surfaces.
Received on Thursday, 30 May 2013 15:23:30 UTC

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