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Re: Opacity 0-1: Bad Idea?

From: Chris Lilley <chris@w3.org>
Date: Sun, 11 Nov 2001 23:25:53 +0100
Message-ID: <3BEEFAF1.B334732@w3.org>
To: lordpixel@mac.com
CC: www-style@w3.org


Andy wrote:
> 
> Dmitry Beransky wrote:
> >
> > Actually, I can see why Kevin might have thought so.  The spec says:
> >
> >    Any values outside the range 0.0 (fully transparent) to 1.0
> >    (fully opaque) will be clipped to this range.
> >
> > using '0.0' and '1.0' instead of '0' and '1'. Strictly speaking, this
> > implies that the precision is only to the first decimal position.

No, it does not. Please read the grammar. 0.0 and
0.000000000000000000000000 are exactly equivalent. 0.0 to 1.0 defines
very precisely the allowable range (largest and smallest values) and
does not define the allowable precision.

> This is all very nice, but ultimately, it would be *much* clearer as a percentage:

Not really; percentages in CSS are typically percentages of something
else, and are transformed to computed values by finding that something
else and multiplying out by the percentage.

> No one says "that pane of glass in that window is semi-opaque". It would
> always be "transparent" (or translucent!). Its just not English!

In fact the term opacity has a long usage in the (English language)
computer graphics literature at least back to 1963, and probably
further.
> 
> Since CSS3 is not final, now's the ideal time to change!

Firstly, there are no particularly good reasons presented to change.

Secondly, the property is already in a W3C Recommendation (SVG 1.0), it
is thus final; and being included into CSS3 to allow its use in areas
other than purely graphical.
http://www.w3.org/TR/SVG/masking.html#OpacityProperty

Thirdly, there are already a substantial number of implementations of
this property, in both renderers and authoring tools.

-- 
Chris
Received on Sunday, 11 November 2001 17:25:55 GMT

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