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Re: [css3-background] should specify color space for box-shadow blurring

From: Alan Gresley <alan@css-class.com>
Date: Sun, 02 Oct 2011 08:27:36 +1100
Message-ID: <4E8785C8.6080305@css-class.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Brian Manthos <brianman@microsoft.com>, "L. David Baron" <dbaron@dbaron.org>, "www-style@w3.org" <www-style@w3.org>
On 2/10/2011 1:21 AM, Tab Atkins Jr. wrote:
> On Sat, Oct 1, 2011 at 4:55 AM, Alan Gresley<alan@css-class.com>  wrote:
>> There is not premultiplied and non-premultiplied spaces.
>> There is only premultiplied and non-premultiplied traversal (paths) of sRGB
>> colorspace (with full opacity). A gradient from yellow to blue has a
>> midpoint of gray (#797979).
> Incorrect.

Incorrect in which way?

1. A gradient from yellow to blue has a midpoint of gray (#797979).

2. premultiplied gradients do not transverse colorspace but only change 
in an alpha plane that is extrapolated out from sRGB colorspace.

>>> sRGB
>>> vs linearRGB is a completely different story.
>> I would like to know what linearRGB is? Should I go off searching.
> Going searching would be a good first step.  It has to do with gamma
> correction. There are plenty of decent sites talking about the issue.
> ~TJ

Perhaps here,


and here.


Which transforms a 3D space into 2D representation.


   | Based on the work of MacAdam, the CIE 1960, CIE 1964,
   | and CIE 1976 color spaces were developed, with the
   | goal of achieving perceptual uniformity (have an
   | equal distance in the color space correspond to
   | equal differences in color). Although they were
   | a distinct improvement over the CIE 1931 system,
   | *they were not completely free of distortion*.

There is a distortion since it is 2 dimensional representation of 
something that is 3 dimensional.

It's only after seeing something in 3D that you truly understand that 
Lightness itself (as in HSL) is orientated on a difference axis to the 
Hue and Saturation components of sRGB colorspace (view in WebKit).


Alan Gresley
Received on Saturday, 1 October 2011 21:28:10 UTC

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