Re: [css-compositing] some proposals

Hi Cyril,

can you describe the structure in more detail?
Is it:

<g alpha-compositing='dst-atop'>

<circle>
<circle blending='plus'>

</g>

or

<circle>
<circle alpha-compositing='dst-atop' blending='plus'>

or a different one?

Rik

On Sun, Nov 20, 2011 at 4:29 PM, Cyril Concolato <
Cyril.Concolato@cisra.canon.com.au> wrote:

>  Hi Rik, Alex,
>
>
>
> Just to make sure I understand the proposal. What would happen if you
> apply the ‘dst-atop’ compositing operator with partially transparent
> objects together with say a ‘plus’ blending operator. I understand that the
> ‘plus’ would only apply on the intersection but I’m not sure about the
> maths. Would you compose the equations, in which order? It doesn’t look
> like you can consider that the result of the (alpha-)compositing becomes
> the source (or destination) of the (color-compositing) blending ,does it?
>
>
>
> Regards,
>
> Cyril
>
>
>
>
>
> *From:* Rik Cabanier [mailto:cabanier@gmail.com]
> *Sent:* Friday, 18 November 2011 4:11 PM
>
> *To:* www-svg; public-fx@w3.org
> *Subject:* [css-compositing] some proposals
>
>
>
> Last week I sent out some ideas to update the SVG composting spec:
> http://www.w3.org/TR/SVGCompositing/.
>
> Some people suggested some improvements which I integrated.
>
>
>
> Here is the updated list of proposals:
>
> 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.
>
> Porter-Duff will continue to use the existing comp-op property.
>
>
>
> Blending describes how the top image will 'blend' with its underlying
> colors. The result of this is a new blended image. In the Adobe imaging
> model and the existing SVG compositing spec it is assumed that this blended
> image is composited with src-over.
>
> However, there are use cases where you might not want 'src-over'. To
> facilitate other composting operators, we will introduce a new keyword
> 'blend-mode'.
>
>
>
> b. simplify Porter-Duff
>
> -remove the clip-to-self property. The default behavior becomes
> 'clip-to-self: object'.
>
>
>
> c. complete blend modes
>
> - add the following missing blend modes: hue, saturation, color &
> luminosity
>
> - define 'normal' as the default blend mode
>
>
>
> d. update knockout
>
> - change the value to be more descriptive. The new value
> ('replace'/'preserve') is confusing.
>
> - provide a better description + correct the compositing formula
>
> - knockout will only affect groups that use the new 'blend-mode' operator
>
>
>
> e. update enable-background
>
> - remove the ability to set up x, y, width & height.
>
> - clarify the description and refer to the filters spec which already
> defines this parameter
>
> - replace the keyword with 'isolate' which is Adobe's equivalent.
> 'isolate: isolated' = 'enable-background: new'. Keep the existing parameter
> for backward compatibility.
>
> - Any comp-op apart from 'src-over' will establish a new stacking context.
>
>
>
> f. update all the formulas on the page
>
> - fix incorrect math
>
> - always do the math with pre-multiplied alpha.
>
>
>
> g. replace 'src'/'dst' in the spec with 'source'/'dest'
>
>
>
> Let me know if I missed something.
>
>
>
> Rik
>
>
>
>
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