Re: Mask property syntax and CSS <image>

On Mon, Aug 6, 2012 at 7:42 PM, Dirk Schulze <dschulze@adobe.com> wrote:

>
> On Aug 6, 2012, at 7:14 PM, Brian Birtles <bbirtles@mozilla.com> wrote:
>
> > Hi Rik,
> >
> > (2012/08/07 11:02), Rik Cabanier wrote:
> >>       mask: url(#circleElem); // alpha
> >>
> >>    and, likewise,
> >>
> >>       mask: linear-gradient(...); // -webkit-mask makes this alpha
> >>       mask: url(#gradientElem); // alpha
> >>
> >>
> >> I don't follow this. Why do these 3 examples use alpha?
> >
> > Ignore the first example. I think we're going to require using element()
> > syntax for directly referencing SVG elements as image mask sources so
> > the first example is invalid.
> >
> > The second one, 'linear-gradient()' uses a default of alpha for two
> reasons:
> >
> > * Because -webkit-mask does. That's not such a big concern to me but
> > obviously if we change this behaviour it makes it harder for content
> > authors who are relying on the current behaviour of -webkit-mask to
> > transition to the new behaviour.
> >
> > * More importantly, for implementers it means that all <image> values
> > can be treated the same (since gradients are a type of <image> value).
> >
> > For the third example, IF we decide that a CSS gradient defaults to
> > alpha, then I think we should be consistent when pointing to an SVG
> > gradient.
> >
> >> I think we need feedback from designers/tool makers.
> >
> > That would be good, as well as web developers and other content authors.
> >
> >> I know many designers use the same outlines of artwork as a mask. My
> >> fear is that since luminosity is not the default and misunderstood, it
> >> will end up not being implemented.
> >
> > That's an important consideration. However, I think all major browser
> > vendors have already implemented luminosity for SVG though so we should
> > be ok right?
> Yes, and Rik is just thinking about the new features like referencing a
> painted object, image or paint server that are not implemented anywhere.
>
> There is the exception for WebKit which does already implement image and
> gradient masking. And WebKit already does use alpha as default value.
> Therefore I wouldn't worry that implementations don't follow. And authoring
> tools would be wise to follow implementations

However, if the tools creator or designer believe that luminance is what
> they want, they just need to add the keyword 'luminance'. Like I said
> before, we can add an issue to the spec that it needs to be considered to
> change the default value. The spec still could get to CR, since the
> implementation feedback is required.
>

I think this is a good course of action.


>
> And I agree that paint servers, element() or referenced images should be
> used as mask with the same default value. Mask elements on the other side
> should use luminance as default value for legacy reasons. We wouldn't break
> any content from current authoring tools. Maybe we can agree on that
> statement first and solve 'alpha'/'luminance' for the first part later. I
> don't think that we need to many discussions at this point about a default
> value.
>

OK. Let's go with that for now.


>
> Greetings,
> Dirk
>
> >
> > Brian
> >
>
>