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Re: [css3-background] box-shadow spread radius and rounded corners

From: Brad Kemper <brad.kemper@gmail.com>
Date: Sun, 16 May 2010 17:20:57 -0700
Cc: Alex Meiburg <timeroot.alex@gmail.com>, www-style list <www-style@w3.org>
Message-Id: <E4BACC21-1199-499C-8C0B-8DE16915B419@gmail.com>
To: Brendan Kenny <bckenny@gmail.com>

On May 16, 2010, at 3:28 AM, Brendan Kenny wrote:

> Spread is instead an entirely graphic effect, originally defined by
> the needs of print, but with definite use cases today. I think the key
> is in these cases, because outside of simulating shadows, it is
> primarily used to add an offset shape (or path), to add a second
> border (which was mentioned as one natural outcome from where the spec
> is going right now), or to add a pseudo inner or outer glow.
> 
> Spread is used to make bigger shadows _or_ it is used to make
> something not very shadow-like at all; the rasterized results can look
> similar (hence the historical use of spread to create drop shadows),
> but the motivations are totally different.

It is used to offset the edge of the shadow, without increasing the blurriness of the shadow, and without having the _ change_ to width/height based on the proportions of the element (it is instead an even increase all the way around). While the terms "spread" and "choke" originated with the practice of filling gaps between printed colors, the usefulness of the effect for shadows is well proven. This usefulness is not based on any need to re-create nature, it is based on the need to take artistic license in order to create a desired visual effect.

It is especially useful for text, if we can ever bring it over to text-shadow too, because it allows the shadow to be seen on all sides of the character (so that a white letter against a dark shadow is visible, for instance), without over-blurring the letter shape. But its usefulness carried over to rectangular shapes too. When I spread the shape of a rectangle, it is not just because I want a bigger shadow; it is because I want the the edge moved outward, usually to allow some of the shadow to show on the other side of the object too without making it blurrier. It is an artistic need, and block shadow is an artistic effect.

Received on Monday, 17 May 2010 00:21:33 GMT

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