RE: SVG 2 rendering model

An implementor always has to do this anyway.
The only difference is if the bitmap is filled with transparent black (= isolated) or the backdrop (=non-isolated)

In PDF, this information comes from the bbox in the transparency group. Regardless of isolation, the buffer is created. (See 11.4.3 in the PDF spec)

Rik

> -----Original Message-----
> From: Leonard Rosenthol
> Sent: Thursday, August 02, 2012 1:09 PM
> To: Rik Cabanier; Nikos Andronikos; public-svg-wg@w3.org
> Subject: Re: SVG 2 rendering model
> 
> On 8/2/12 3:34 PM, "Rik Cabanier" <cabanier@adobe.com> wrote:
> 
> >Hi Leonard,
> >
> >> The problem with making isolated the default is that it will impact
> >> performance for all of the normal cases.
> >Isolated is faster since you don't have to composite all the group to
> >get the background.
> 
> But you DO have to create an "offscreen buffer", composite the entire
> group into that, and then blit the entire "offscreen" back.   So you're
> clearly using more memory and time than simply putting bits into the existing
> buffer.
> 
> 
> >The compositing spec specifies the order in which filters and
> >compositing happens.
> >The filters spec should say if the stacking group it creates is
> >isolated or not. I believe people don't want it to be isolated (and can
> >post some examples if needed)
> 
> But how would you apply a filter to a group that has already been blended
> into the background?  The result is certainly going to be different - which
> may be good or bad.
> 
> I would think that given a group with a filter applied to it, you have to make
> that specific group isolated, apply the filter, and only then blend it to the
> background.
> 
> Leonard

Received on Thursday, 2 August 2012 20:25:29 UTC