W3C home > Mailing lists > Public > www-svg@w3.org > December 2013

RE: [filter-effects] Blending without compositing

From: David Dailey <ddailey@zoominternet.net>
Date: Thu, 12 Dec 2013 21:35:41 -0500
To: "'Nikos Andronikos'" <nikos.andronikos@cisra.canon.com.au>, "'Dirk Schulze'" <dschulze@adobe.com>, <public-fx@w3.org>, "'www-svg'" <www-svg@w3.org>
Message-ID: <002501cef7ac$04903bc0$0db0b340$@net>
Whatever ya'll decide here, there are a few use cases that have been with us
since the beginning of time:

 

Additive and subtractive color models:

 

See the first two (from top left) illustrations at 

http://cs.sru.edu/~ddailey/canterbury/V9a.svg

 

in ASV (so robust it was!)

or In Opera (12.16 - is there a later version I should be using?)

 

Things are good!

 

But the drawing is disturbingly complex (though not nearly so awful as what
other people do  -- see for example
http://en.wikipedia.org/wiki/File:SubtractiveColor.svg which breaks every
conceivable concept of accessibility whether ya'll like those concepts or
not)

 

Then take a peek in IE 11 (which at least seems to understand what an author
intended with regard to feComposite and feBlend) but seems to barf on the
idea of replicated filters applied to one another?

 

IE11 gets a passing grade (D)

 

Of course it may be the spec that is flunking rather than the browsers, but
my goodness! How hideous the discrepancies are!

 

Now turn your attention to Chrome (I don't really know what Chrome likes to
call itself now - I found myself in an upgrade path no doubt controlled by
Samsung or Hitachi - I don't know who) Chrome 31.0.1650.63 m (which probably
tells the NSA the exact machine in the universe I was using when I repeated
the experiment) maybe it is Chromium maybe it is Bling, maybe it is the
goofy banner thing that IE implemented that got standards folk so nutty in
the 1990's)) , Oh my! I could not have figured out how to make this
particular result happen if I wanted it to! Extra credit to anyone who can
make this happen across browsers (on purpose!).

 

Safari at least sees all the circles, but it just gives up altogether on the
filters.

 

Firefox is so terribly unhappy with the example that it refuses to try to
render any more than two of the circles!

 

All browsers respectfully disagree! It is exactly the sort of example I like
since no two browsers do the same thing! Additional extra credit for the
hall-of-fame-of-browser-breakers for things that make all eight browsers
disagree (eight?).

 

All I want to do is draw additive and subtractive models of color in as
simple a way as possible!

 

Dear standards-writers. please make sure that in your next version of SVG (I
am patient and can wait for 3.0 if needed) there is a way to do this. Please
let me know how to as well, so that if I write articles about how to do it,
the spec won't change out from under me - not that that would ever happened
of course!

 

Perennial cheer and occasional irony.

David

 

 

 

 

From: Nikos Andronikos [mailto:nikos.andronikos@cisra.canon.com.au] 
Sent: Thursday, December 12, 2013 6:45 PM
To: Dirk Schulze; public-fx@w3.org; www-svg
Subject: Re: [filter-effects] Blending without compositing

 

On 12/12/2013 5:21 PM, Dirk Schulze wrote:

Are we trying to preserve backwards compatibility here? e.g. keep an option
for the (incorrect) double composite and add an option for no composite? 

 

 

[DS] Yes, backwards compatibility is important. Do I understand your comment
correctly that you also don't want to add compositing modes to feBlend? In
this case I suggest a new attribute called composite = "true | false" (I
would like to have a boolean attribute but that needs changes on SVG2....
lets see if we get that before LC.)

 

 

This was discussed at this mornings telcon, but just for closure:
Yes you do understand me correctly =)
I don't think adding compositing operators to feBlend would be useful if the
implementation is going to be different than the compositing and blending
spec (because the double contribution of the backdrop needs to be retained
for src-over).

And on that note, I think it would be a good idea to add a note to Filter
Effects explaining that the double contribution of the backdrop will occur
if 'no-composite' is enabled.

Nikos
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Received on Friday, 13 December 2013 02:36:38 UTC

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