W3C home > Mailing lists > Public > www-style@w3.org > October 2009

Re: [CSS-color] gamma

From: Chris Murphy <lists@colorremedies.com>
Date: Tue, 20 Oct 2009 14:50:34 -0400
Cc: Dave Singer <singer@apple.com>
Message-Id: <6D23D8BE-009F-4407-A145-7A67D8453AD3@colorremedies.com>
To: W3C style mailing list <www-style@w3.org>
http://lists.w3.org/Archives/Public/www-style/2008Jul/0229.html

Looks like it's in the last call just due to how long everything  
takes. But hopefully it can removed before it goes to Candidate  
Recommendation.


And for that matter, before this moves onto Candidate Recommendation,  
See section 9 "Call for Implementations of dropped features."

It's unclear to me why long ago the gamma section wasn't treated the  
same way as section 9 has been. The argument I read recently for  
dropping these ICC features is that no developer has implemented them.  
This suggests the CSS spec reflects best practices of what's already  
been implemented, rather than suggesting what the best practice should  
be. Yet to my knowledge no browser on Mac OS has ever implemented the  
gamma section and even to this day no browser on Mac OS conforms to  
this section by default.

The reading of the spec right now causes a departure in color space  
between images and CSS/HTML content. Section 4.2.1 applies only to CSS/ 
HTML colors, not to images. And Section 4.2.1 implies color conversion  
in all cases from sRGB to display space, on all platforms. Yet the  
absence of a similar assumption for images, means images and CSS can  
be out of sync and yet the spec is being followed. Seems like a bad  
idea for color consistency.




Chris Murphy



On Oct 19, 2009, at 5:43 PM, Dave Singer wrote:

> Maybe I am being dense, but why do we have this section at all?
>
> It seems that colors should be expressed in a known color space, and  
> that if the output device or display has any different  
> characteristics (e.g. different gamma, or is CMYK because it's being  
> printed), then color space conversion needs to take place.
>
>
> On Oct 19, 2009, at 13:58 , Chris Murphy wrote:
>
>> Re: Editor's Draft 7 August 2008
>> http://dev.w3.org/csswg/css3-color/#gamma
>>
>> This contains an obsolete recommendation for Mac OS: a.) which  
>> hasn't used QuickDraw for some time; and b.) starting with 10.6  
>> display TRC is defined by a gamma 2.2 function. Correction is no  
>> longer required.
>>
>> Mac using QuickDraw should be changed to Mac OS 10.5 and older, and  
>> the minimum handling recommendation can remain.
>>
>>  And a new OS class Mac OS 10.6 and newer with a minimal handling  
>> of "none" should be added to the list.
>>
>>
>> Chris Murphy
>> Color Remedies (TM)
>> New York, NY
>> ----------------------------------------------------------------------
>> Co-author "Real World Color Management, 2nd Ed"
>>
>>
>
> David Singer
> Multimedia and Software Standard, Apple Inc.
>
Received on Tuesday, 20 October 2009 18:51:08 GMT

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