W3C home > Mailing lists > Public > public-fx@w3.org > April to June 2013

Re: [filter-effects] feBlend filter (was: Re: [css-filters] feBlend filter)

From: Dirk Schulze <dschulze@adobe.com>
Date: Wed, 29 May 2013 20:35:55 -0700
To: Rik Cabanier <cabanier@gmail.com>
CC: "public-fx@w3.org" <public-fx@w3.org>, www-svg <www-svg@w3.org>
Message-ID: <0CDDA17B-BBCF-4B4F-8C88-74B0A1723C37@adobe.com>

On May 29, 2013, at 7:41 PM, Rik Cabanier <cabanier@gmail.com> wrote:

> 
> 
> On Wed, May 29, 2013 at 7:14 PM, Dirk Schulze <dschulze@adobe.com> wrote:
> 
> On May 29, 2013, at 6:59 PM, Rik Cabanier <cabanier@gmail.com> wrote:
> 
> >
> >
> > On Wed, May 29, 2013 at 5:33 PM, Dirk Schulze <dschulze@adobe.com> wrote:
> >
> > On May 29, 2013, at 5:05 PM, Rik Cabanier <cabanier@gmail.com> wrote:
> >
> > [snip]
> > > If we replace the formulas with the one without compositing, what would it mean for blending two intermediate results?
> > > The result would exclude compositing completely. It is unclear how this can be done.
> > >
> > > You'd have to explicitly call feComposite on the blended result.
> >
> > feComposite uses the alpha channel of the two input primitives. feBlend the same, just that you loose the alpha channel on the result of your feBlend (since the state is unclear).
> >
> > Why would you lose the alpha channel? Blending doesn't affect source alpha (ár = ás)
> >
> > If the next primitive after feBlend is feGaussianBlur, what would be blurred on the alpha channel? I do not think that you can easily separate blending from compositing inside a SVG filter tree.
> >
> > Sure you can. feGaussianBlur would work the same except that the source colors are now blended and alpha is unaffected.
> 
> If ar = as, why would the alpha channel would not be affected on blurring?
> 
> If you do a gaussianBlur, its input regardless of it's blended or not, will always have the same alpha values.
> A good question is if blurring after blending makes sense of course :-)

You blur all channels, including the alpha channel for feGaussianBlur. Since you say ar = as, this basically means source-in, doesn't it?

Greetings,
Dirk
Received on Thursday, 30 May 2013 03:36:41 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 19:49:45 UTC