- From: Rik Cabanier <cabanier@gmail.com>
- Date: Mon, 7 Nov 2011 19:38:44 -0800
- To: www-svg <www-svg@w3.org>, public-fx@w3.org
- Message-ID: <CAGN7qDBT+Smj2ZmofN4wuw6uYJ1c=qpetU+c9-_9qWWNQ7fSxg@mail.gmail.com>
All, I have some proposals for the SVG compositing spec: http://www.w3.org/TR/SVGCompositing/. We can have a conversation on each item and if there is a general consensus, I will start to update the compositing spec. a. split up the spec in 2 sections: Porter-Duff & Blending. Porter-Duff are compositing primitives that describes how 2 images (src+dst) can be merged. Blending describes how the top image will 'blend' with its underlying colors. The result of this is a new blended image. So far, we assume that after blending, this image is composited with Porter-Duff src-over. I am tempted to split the spec, but keep the comp-op keyword the same for both PD and blending. This does imply that you won't be able to do xor or src-in with blended content. Does anyone believe that this is a use case? b. simplify Porter-Duff - remove the clip-to-self property. The default behavior becomes 'clip-to-self: object'. Does anyone believe that 'clip-to-self: canvas' is useful? It feels strange to have that option in SVG. - 'enable-background' does not apply. Children with blending will composite up to the group with PD blending. (In effect, PD will always imply 'enable-background: new') - 'knock-out' on the nearest ancestor with blending does not apply. If it has 'knock-out: preserve', the group with the PD compositing operator will still knock out. - Simon Fraser expressed concern that this compositing operator required access to the entire background image. Maybe we should specify that all PD blending should be done inside a group that has 'enable-background: new'. c. complete blend modes - add the following missing blend modes: hue, saturation, color & luminosity - specify that the result of blending is always composited using src-over - potentially: change the default of enable-background to 'new' if you specify a blend mode so a new stacking context is established. Most people want a new stacking context and it also makes it easier and less memory intensive to process for a SVG processor. d. Add a new blend mode: 'normal' - this is the default blend mode on all groups and leafs. - similar to PD's src-over except it doesn't create a new stacking context - 'enable-background' and 'knock-out' apply e. update knockout - change the value back to a boolean value from 'replace'/'preserve'. The new value is confusing. - provide a better description + correct the compositing formula f. update enable-background - remove the ability to set up x, y, width & height. I believe there's already consensus on this. - clarify the description and refer to the filters spec which already defines this parameter - maybe replace the keyword with 'isolate' which is Adobe's equivalent. 'isolate: true' = 'enable-background: new'. I think this is a little easier to grasp and it is also familiar to designers. Let me know of any concerns. Rik
Received on Tuesday, 8 November 2011 03:39:15 UTC