W3C home > Mailing lists > Public > www-svg@w3.org > March 2011

Re: SVG Compositing operators backported?

From: Alex Danilo <alex@abbra.com>
Date: Fri, 18 Mar 2011 07:40:18 +1100
Message-Id: <6RY7IL.HSES4CUU8INM@abbra.com>
To: Alexandre Prokoudine <alexandre.prokoudine@gmail.com>
Cc: www-svg <www-svg@w3.org>
Hello,

--Original Message--:
>On Thu, Mar 17, 2011 at 6:23 PM, Jasper van de Gronde wrote:
>> Hi,
>>
>> I just heard that the SVG Compositing spec is nearly finished. This is
>> very good news, as I think it's a marvelous addition to SVG! However,
>> I'm wondering whether any of the new operations will be "backported" to
>> filters?
>>
>> For implementations this should be next to no (additional) work, but
>> having it formalized would help in making sure that behaviour is
>> consistent across different renderers.

There is no technical reason to limit the modes to just the comp-op
property.

At the time filters were done, the equations for the other blend
modes were not published. We worked very hard to derive those
equations in the compositing spec. without any assistance from
company 'A'. Eventually the equations we derived proved to be
correct. So at this time, it probably makes sense to add them
to filters. The spec. effort to do so will be separate to the
compositing spec. itself due to the W3C process, since it's too
late to add anything to the compositing spec. But I'm sure the
group will all agree this is a useful change.

>Chris asked me to repost it to this list from inkscape-devel@, so here goes :)
>
>> The comment that you love it would be good to post there too :) especially especially if your email includes the word "because".
>
>May I try? :)
>
>http://www.osnews.com/story/7102/Interview_with_Everaldo_and_Jimmac/page1/
>
>"Everaldo: OK, in the beginning I used Corel Draw 9, running in Linux
>and gimp, but as Corel stopped developing corel for Linux and version
>9 did not have a good support for SVG, I moved to adobe illustrator,
>which up to this moment proved to be the best software to draw
>vetorial graphics in SVG and photoshop replaced gimp. Unfortunately
>the SVG generated by illustrator is not a 100% compatible with KDE.
>The problem is the transparency modes "multiply" and "hard light" are
>not understood by KDE, they are very useful and needed for the
>creation of light and shadow in my icons."
>
>That was in 2004. Seven years later we are finally close to having
>this bloody nuisance fixed.

Agreed, I was pushing the compositing spec. back in 2002 and did
the math for the modes back then. The delay to this point in time
was unavoidable and quite annoying to say the least...

To add to Everaldo's comment - when you export SVG from Illustrator
it uses an adobe namespace on a property called 'adobe-blending-mode'
which is the same mechanism as the 'comp-op' operator. Filters
are not used for the export.

In effect, if you grab a text editor with an Illustrator export
file, you should be able to go:

s/a:adobe-blending-mode/comp-op/g

and voila, all the blend modes will magically work in a viewer that
supports the compositing spec.

>However like Jasper I'm concerned about relation to feBlend. The
>roadmap says Filters will become recommendation in July 2012. We've
>been bitten by a change in the SVG wind in the past (flowed text) and
>we are very cautious about experimenting ever since then, so it's
>probably chicken-egg situation all over again.

It's a shame what happened with text flow since it was a really
good feature.

However, that was in a Working Draft, and as such is not guaranteed
to be stable.

The compositing spec. is in Last Call, so it will be in Candidate
Recommendation soon (4 weeks or so) and that is the point at which
implementers should seriously implement what's in there. Before CR
is speculation.

The reason compositing is now a separate module like many other
modules is due to the delays that happened with 1.2, text flow
being an unfortunate victim too. Personally I'd like to see the
text flow work re-used and that effort may happen depending on
whether the CSS/SVG harmonization works well. At the moment CSS3
has a bunch of new text flow ideas, some truly weird (like using
z-index to manage text exclusion regions), so there is likely
to be a long painful debate about that sort of functionality
very soon.

I would highly encourage people to implement the compositing
spec. since it provides great features that SVG really needs.

Alex

>Alexandre Prokoudine
>http://libregraphicsworld.org
>
>
>
Received on Thursday, 17 March 2011 20:41:11 GMT

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