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Re: shadow through transparent background (was Re: Shadow knockout)

From: Alan Gresley <alan@css-class.com>
Date: Thu, 27 Jan 2011 20:41:48 +1100
Message-ID: <4D413DDC.7000201@css-class.com>
To: "Eric A. Meyer" <eric@meyerweb.com>
CC: www-style@w3.org, Brad Kemper <brad.kemper@gmail.com>
CC Brad Kemper.

On 27/01/2011 5:06 PM, Alan Gresley wrote:
> On 27/01/2011 3:05 PM, Eric A. Meyer wrote:
[snip]
>> Or is it that because
>> backgrounds are transparent by default, it's thought the shadow
>> shouldn't be visible behind the content because that could create
>> legibility problems?
>
>
> Not if it's done carefully. Also a box-shadow does not have to be dark.
> If you offset the box-shadow enough, you can see how the full box-shadow
> is rendered. This means that a full box-shadow is painted first and then
> implementations have to apply a mask on the shadow where it intersects
> the border-box of the background.


This is a demo of how a box-shadow through a transparent background 
would look like.

<http://css-class.com/test/temp/box-shadow-transparet-bg.htm>


The concept is that the more transparent color that you add over the 
dark background, the lighter the combined transparent box-shadow and 
transparent background-color appears over a dark background. The 
combined colors must be close together in hue for this affect to happen.

If a light background is used instead, the opposite happens where the 
combined transparent box-shadow and transparent background-color appears 
darker over a light background.

On a side note, if the current specs stays the same, then authors will 
surely hack the affect by a similar method as I have used to demonstrate 
the concept.


-- 
Alan http://css-class.com/

Armies Cannot Stop An Idea Whose Time Has Come. - Victor Hugo
Received on Thursday, 27 January 2011 09:49:10 GMT

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