Re: [filter-effects] Blending without compositing

On Fri, Dec 6, 2013 at 5:16 AM, Dirk Schulze <dschulze@adobe.com> wrote:

> Hi,
>
> The SVG WG resolved at the F2F in Tokyo this summer that <feBlend> in
> Filter Effects should support blending without compositing. This shall
> avoid double compositing as it can happen in combination with
> BackgroundImage today. [1]
>
> We did have some difficulties to define the exact way to disable
> compositing. There are two different proposal so far:
>
> 1) Support all compositing operators on <feBlend>
>
> The idea is that we actually do not disable compositing but allow the
> author to use a different compositing operator. The ‘mode’ attribute could
> be extended to support compositing modes as well:
>
> <blending> = [normal | multiply | screen | darken | lighten] || [over | in
> | out | atop | xor]
>
> which could look like this:
>
> <feBlend mode=“screen atop” in2=“BackgroundImage” />
>

Unfortunately, this does not solve the problem. We want to option to skip
the compositing step, not to replace it with another one.


>
> (The compositing values could be replaced by the keywords used by Canvas.)
>
> 2) Create new attribute ‘compositing'
>
> SVG does not support boolean attributes yet. Therefore the attribute
> ‘compositing' would need values like ‘composite’/’no-compositing’ or simply
> ‘true’/‘false’.
>
> With this attribute the compositing step can just be omitted completely or
> switched to source-over compositing following the formulas from CSS
> Compositing and Blending.
>
>
> Any preferences?
>

I think only option 2 is viable.


>
> [1] http://dev.w3.org/fxtf/filters/#issue-9d31c6c7
>