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Re: [css3-color] New last call for comments on CSS Color

From: Alan Gresley <alan@css-class.com>
Date: Thu, 30 Sep 2010 02:27:03 +1000
Message-ID: <4CA368D7.3040504@css-class.com>
To: Chris Lilley <chris@w3.org>
CC: www-style@w3.org, Dave Singer <singer@apple.com>
Chris Lilley wrote:
> Hello www-style,
> 
> Dave Singer wrote:
>> Is the HSL full-range (0-255 luminance) or video-range (16-235 
>> luminance)?  This makes a BIG difference.
> http://lists.w3.org/Archives/Public/www-style/2008Jul/0467.html
> 
> I notice that there was no response to this part of your comments. The answer is that the HSL values are full range not video range, as the algorithm 'to translate HSL to RGB' and examples given in section 4.2.4 makes clear.
> 
> http://dev.w3.org/csswg/css3-color/Overview.html#hsl-color
> 
> Therefore, no specification change was necessary. Dave, please respond to say that you agree with this conclusion.


Upon researching color, OS and display devices I see that since about 
2006 there have been display devices that extends outside the sRGB 
gamut. These display devices use scRGB color space [1]. One example is 
HDMI [2] with output as xvYCC [3] [4]. With the launch of Windows 7 
with 64-bit (use 48-bit color depth) OS, an OS can now generate colors 
in scRGB color space. I do not know quite how the technology works 
(like device pixels) but it allows negative values and very high values.

Via Wikipedia:

   | scRGB is a wide color gamut RGB (Red Green Blue) color space
   | created by Microsoft and HP that uses the same color primaries
   | and white/black points as the sRGB color space but allows
   | coordinates below zero and greater than one, the full range is
   | -0.5 through just less than +7.5.


sRGB color space show about 35% percent of the color we perceive where 
scRGB extend this to about 70% of the colors we perceive and maps to 
the CIE 1931 xy chromaticity diagram differently to Adobe's Wide Gamut 
RGB color space.


I notice that I can use this in all implt that support RGB.

   rgb(-10, 275, 120)

This shows as this.

   rgb(0, 255, 120)


Clamping already works as seen in the above example.


The reason for the last call comment is to suggest some prose in the 
spec in CSS3 color that says both HSL and RGB can have values outside 
the known 0 to 255 range.



1. <http://en.wikipedia.org/wiki/ScRGB>
2. <http://en.wikipedia.org/wiki/High-Definition_Multimedia_Interface>
3. <http://en.wikipedia.org/wiki/XvYCC>
4. 
<http://www.sony.net/SonyInfo/technology/technology/theme/xvycc_01.html>




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

Armies Cannot Stop An Idea Whose Time Has Come. - Victor Hugo
Received on Wednesday, 29 September 2010 16:27:39 GMT

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