Re: [css3-background] possibly too late for last call, but: background-opacity?

2009/10/16 Robert O'Callahan <>

> Out of all the ideas presented so far, new image functions sound best to
> me, e.g.
> background-image: image-opacity(url(foo.png), 0.3);
> background-image: image-offset(url(foo.png), 100, 0);
> background-image: image-rect(url(foo.png), 100, 0, 100, 200);
> These are animatable with transitions, compose well and don't require
> changes to CSS fundamentals.

Not that well, actually.

1) You need to repeat the URI every time, and you cannot cascade
independently the image and its opacity.
2) You cannot use that for "drop-shadow" (because the drop-shadowed
border-image would be clipped, making it no better than Photoshop)
3) You cannot use that for content-only effects (unless you hack "content")

> For arbitrarily complicated stuff, I recommend SVG filters with additional
> named source images representing the CSS components of the source element.
> We probably need to figure out a mechanism so that filters can be
> parameterized with CSS values though --- both for ease of reuse and easy
> animation. Something like
> filter: url(effects.svg#LSD), 10, 10, 2;
> effects.svg contains
>   <feOffset in="CSSBackground" x="$1" y="$2"/>
>   <feColorMatrix type="hueRotate" values="$3"/>
There's an SVG Param spec on the filter side, we only need syntax on the CSS
side. But I would object to that use of comma, I believe there are use-case
for multiple filters.

Besides, we still need to define the processing of "filter" in the CSS
realm. We may go with "what mozilla currently does" or "what's more
SVG-like" or "what's more author-friendly". We may need to think of the IE
side of "filter" too.

> Rob
> --
> "He was pierced for our transgressions, he was crushed for our iniquities;
> the punishment that brought us peace was upon him, and by his wounds we are
> healed. We all, like sheep, have gone astray, each of us has turned to his
> own way; and the LORD has laid on him the iniquity of us all." [Isaiah
> 53:5-6]


Received on Saturday, 17 October 2009 15:28:09 UTC