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Re: [css-images][css-compositing] Blurring an elementís backdrop

From: Rik Cabanier <cabanier@gmail.com>
Date: Thu, 5 Dec 2013 20:42:11 -0800
Message-ID: <CAGN7qDDYMi+7sG_FYm3R830x-9-ivcCCxyz_AWHta=TsfoQ3Mg@mail.gmail.com>
To: Lea Verou <lea@verou.me>
Cc: Michael Mullany <michael@sencha.com>, Dean Jackson <dino@apple.com>, "public-fx@w3.org" <public-fx@w3.org>, www-style list <www-style@w3.org>, Stefan Craciun <scraciun@adobe.com>
In going with Lea's comment that authors equate backdrop with blending, I
propose the following new property:

backdrop-blur: none | <length>

Length would be the parameter passed into the blur() filter [1].

Specifying this parameter in combination with mix-blend-mode[2], would blur
the backdrop that is available during the blending step. Compositing would
happen as usual.
An alternate would be to extend mix-blend-mode so you can write the

mix-blend-mode: screen blur(10px);

This can still be made compatible with future additions that target parts
of an element.

I'm in the process of creating an experimental windows-only build of
firefox that implements.


1: http://www.w3.org/TR/filter-effects/#funcdef-blur
2: http://dev.w3.org/fxtf/compositing-1/#mix-blend-mode

On Fri, Nov 29, 2013 at 7:51 PM, Rik Cabanier <cabanier@gmail.com> wrote:

> On Thu, Nov 28, 2013 at 10:35 PM, Lea Verou <lea@verou.me> wrote:
>> On Nov 29, 2013, at 12:45, Rik Cabanier <cabanier@gmail.com> wrote:
>> > This might work.
>> > My main concern is that it would overload mix-blend-mode too much since
>> we're also hoping to repurpose it to blend different areas of an element.
>> I'm unsure how we would reconcile that.
>> > Do you have a suggestion?
>> If the syntax for that is what was discussed in the FXTF a while ago, I
>> donít see what the conflict would be. Care to elaborate? :)
> Looking 18 months (!) back on this thread, I proposed the following:
> mix-blend-mode: color-burn(blur(5px))
> Doing it this way will be confusing if we want to blend different
> elements, ie
> mix-blend-mode: background screen, border multiply, content overlay,
> element hue
> Now, each of those *could* theoretically blur the backdrop but that is not
> a strong use case.
> This syntax also gives the impression that your content/border/element has
> the effect applied as opposed to the backdrop.
> Also, as Michael mentioned, simply blurring will not give you the desired
> effect. You often want to soften the backdrop with a white color that's
> blended with soft light or screen.
> He also mentions:
>  we need finer control of the blur opacity/falloff
> I'd prefer if we could create a new property that has nice defaults and if
> we can avoid writing filter chains in CSS.
Received on Friday, 6 December 2013 04:42:40 UTC

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