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Re: [css3-background] A property to control background opacity

From: Simon Fraser <smfr@me.com>
Date: Tue, 24 Dec 2013 11:56:38 -0800
Cc: Rik Cabanier <cabanier@gmail.com>, David <david.email@ymail.com>, www-style list <www-style@w3.org>
Message-id: <270A2BBE-AE3D-4C2B-9FF1-9D6817A70D2B@me.com>
To: Dirk Schulze <dschulze@adobe.com>
Of course!

Given this, I see little utility in a per-background-image background-opacity property.

The only utility for a new background-opacity property that I can see is one that is not per-background-image, but rather applies opacity to the grouped background images and background color,

Simon

On Dec 23, 2013, at 11:57 pm, Dirk Schulze <dschulze@adobe.com> wrote:

> 
> On Dec 24, 2013, at 8:47 AM, Dirk Schulze <dschulze@adobe.com> wrote:
> 
>> 
>> On Dec 24, 2013, at 8:34 AM, Simon Fraser <smfr@me.com> wrote:
>> 
>>> On Dec 23, 2013, at 7:06 PM, Rik Cabanier <cabanier@gmail.com> wrote:
>>> 
>>>> On Mon, Dec 23, 2013 at 4:33 PM, David <david.email@ymail.com> wrote:
>>>> Hello,
>>>> 
>>>> it would be great if a CSS property would be added to control the opacity of the background-image.
>>>> The background-color and its opacity is already controlable via rgba() or hsla().
>>>> The opacity property itself allows just to control the opacity of the whole element.
>>>> 
>>>> We had a short discussion on this at the last F2F during TPAC [1].
>>>> It was unfortunately not minuted. :-(
>>>> 
>>>> During the meeting, people said that this feature has been requested for a long time but for some reason, it never was spec'ed out or implemented.
>>>> 
>>>> Normative text could look as follows:
>>>> The ‘background-opacity’ property
>>>> 
>>> An alternative to this would be to have an image function that gives an image alpha, e.g.:
>>> 
>>> background-image: alpha-image(foo.png, 50%);
>>> 
>>> This would seem preferable to a property that can only apply alpha to background images.
>> 
>> Just to give more alternatives: In WebKit the CSS Image function -webkit-filter() is implemented with the opacity filter function:
>> 
>> background-image: -webkit-filter(foo.png, opacity(0.5));
> 
> Just to give a bit more background: The filter() image function is specified in Filter Effects[1] and allows filtering other CSS Images:
> 
> 	filter( [ <image> | <string> ], <filter-function-list> )
> 
> opacity() is one of the filter functions beside others [2].
> 
> Greetings,
> Dirk
> 
> [1] http://dev.w3.org/fxtf/filters/#FilterCSSImageValue
> [2] http://dev.w3.org/fxtf/filters/#FilterProperty
> 
>> 
>> Greetings,
>> Dirk
>> 
>>> 
>>> Simon
Received on Tuesday, 24 December 2013 19:57:42 UTC

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