W3C home > Mailing lists > Public > www-style@w3.org > July 2008

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

From: Dave Singer <singer@apple.com>
Date: Tue, 22 Jul 2008 09:57:56 +0200
Message-Id: <p0624089dc4ab4281a0c9@[]>
To: W3C style mailing list <www-style@w3.org>

some quick personal comments...

Isn't it enough to say that all colors are in the sRGB color space? 
Isn't it a tautology to say that they should be correctly displayed 
(e.g. an ICC sRGB profile associated with them, and then they should 
be correctly converted to the display color space)?  It feels a bit 
like saying that straight lines should appear straight on the 
display...but at most, 3.1.1 should say basically like the sentence 
above, and not go into details of how one displays sRGB values, gamma 
correction, out-of-gamut color handling, etc.

Is the HSL full-range (0-255 luminance) or video-range (16-235 
luminance)?  This makes a BIG difference.

At 0:31  -0400 22/07/08, Chris Murphy wrote:
>I'm not sure what you mean by "handling out-of range or invalid 
>values." Do you mean a JPEG or text that somehow has an encoded 
>value for red greater than 255? I don't see how that happens in an 
>8bpc world. There simply isn't a place holder for a value greater 
>than 100%.
>But OK, if that can happen (?), then yes instead of the browser not 
>displaying the image or content, or crashing or otherwise dramatic, 
>fine just say anything higher than 100% is only 100% and proceed 
>normally. But I would not call this gamut mapping or clipping, this 
>is error correction in reading the page document or image data.
>I see in the example RGB 300,0,0. Umm, 300 levels don't exist in 
>8bpc. 110%? Doesn't exist. To me this implies floating point where 
>values can be greater than 100% and less than 0%.
>That sRGB 255,0,0 may be out of gamut for my display, but how is 
>this even knowable? You send the color to a CMS and ask it "is this 
>out of gamut or not?" It can be done, but why bother? Just send the 
>value to the CMS and say "display this" and it does the best job it 
>can. Whether it's in or out of gamut doesn't, in my view, need to 
>enter into the equation. The gamut check is a feature in Photoshop, 
>but it's not particularly useful in my view, so I guess I'm just 
>confounded why in and out of gamut colors is even a relevant issue 
>for the developer of a web browser. Tag the data, let the CMS do the 
>Chris Murphy
>On Jul 21, 2008, at 11:59 PM, L. David Baron wrote:
>>On Monday 2008-07-21 23:47 -0400, Chris Murphy wrote:
>>>That whole paragraph.
>>So the normal behavior in CSS for handling out-of-range or invalid
>>values is to treat them as parse errors.  Since device gamuts vary,
>>we don't want to do that here.  So I think the spec needs to say
>>something so that it's clear that the colors specified should
>>somehow be mapped into the device gamut rather than dropped.
>>Is there a more general term than "mapped" that you would prefer?
>>L. David Baron                                 http://dbaron.org/
>>Mozilla Corporation                       http://www.mozilla.com/

David Singer
Received on Tuesday, 22 July 2008 08:11:38 UTC

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