Re: [css3-images] cross-fade()

I *think* you're right.

It should read either:

Then, the start image has a global alpha applied to it equal to (1-p), the
end image has a global alpha applied to it equal to p, and the end image is
then composited over the start image with the plus operation

or

Then, the end image has a global alpha applied to it equal to p, and the end
image is then composited over the start image with the source-over operation

but I could be wrong...

Rik

On Wed, May 4, 2011 at 9:40 AM, L. David Baron <dbaron@dbaron.org> wrote:

> I think the current definition of cross-fade() in
> http://dev.w3.org/csswg/css3-images/#cross-fade-function is
> incorrect.  It defines cross-fade() in terms of the porter-duff over
> operator, which is not symmetric.  This means that cross-fade(A, B,
> 30%) is different from cross-fade(B, A, 70%).
>
> I *think*, though I'm not sure, that the right way to define
> cross-fade is in terms of the plus operator described in section 4.5
> of the original Porter-Duff paper:
> http://keithp.com/~keithp/porterduff/
>
> -David
>
> --
> L. David Baron                                 http://dbaron.org/
> Mozilla Corporation                       http://www.mozilla.com/
>
>