Re: [css4-images] custom blending effects

Hi Dean,

What if we extend the SVG compositing spec to include CSS and provide the
ability to do a custom blend using glsl? It seems pretty straightforward to
come up with a syntax since the notation is basic.
If we combine this with transitions, it seems that this would be powerful
and also enable your use case.

We do need to come up with a way to calculate background in a HTML context
both for compositing and filters...

Rik


On Thu, Nov 24, 2011 at 3:13 PM, Dean Jackson <dino@apple.com> wrote:

> This is a completely half-baked proposal, but I figured it was ok to
> embarrass myself on this list rather than forget about the idea. This is
> definitely not a proposal from Apple as a whole. Just one fool mumbling in
> public.
>
> The cross-fade() function is going to be extremely useful. However,
> cross-fading is one of many blending operations [*]. IIRC SMPTE (and the
> larger SMIL spec) list a set of predefined functions like wipe, iris,
> dissolve, etc.
>
> [*] The terminology is going to be confusing. Typically such operations
> are called 'transitions' but that term already has a meaning in CSS.
> Obviously 'blending' here isn't the same operation as you typically
> associate with compositing and Photoshop-like effects. We're just talking
> about moving from one image to another image over time.
>
> I wonder if we should add another operation to CSS 4 images that allows
> more blending operations. My suggestion would be to allow a CSS Shader with
> three hard-coded inputs (like cross-fade): image1, image2 and amount of
> blend (0 - 1). This would allow for some pretty snazzy effects.
>
> cross-fade would just be the special/common case of e.g.
> image-blend(crossfade, image1, image2, 0.4)
>
> [1] Here's the SMIL set of predefined transitions:
> http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-transitions.html
>
> Dean
>
>
>