Re: [css3-background] blending on 'box-shadow' and 'text-shadow'

On Apr 10, 2012, at 3:52 PM, Rik Cabanier wrote:

> All,
> 
> I'm currently working on the blending specification (http://blogs.adobe.com/webplatform/2012/04/04/bringing-blending-to-the-web/) and someone brought up that a very common use case for blending is drop shadows.
> Some of our applications such as Photoshop, Illustrator and InDesign set the shadow to multiply by default since it provides a more pleasing appearance that can't be done with simple alpha blending. See http://css-tricks.com/dont-use-black-for-shadows/ for a discussion on why this is.
> 
> Would there be interest in an additional keyword to specify blending to 'box-shadow' or 'text-shadow'?
> the syntax could look like:
> box-shadow: 64px 64px 12px 40px rgba(0,0,0,0.4) multiply

Using a different blend mode just for the shadow would place a burden on implementers who use hardware acceleration of various kinds (i.e. most of us now).

Imagine a box-shadow overlapping a playing video. The implementation has to separate the shadow into its own GPU texture, and composite that with a different blending mode from the rest of the element, for every frame of video.

Simon