W3C home > Mailing lists > Public > www-style@w3.org > March 2016

Re: [css-color] wider/deeper colors

From: Simon Fraser <smfr@me.com>
Date: Tue, 22 Mar 2016 17:49:34 -0700
Cc: aaron.www-style-@infinite-source.de, www-style@w3.org
Message-id: <77DFB1F6-C2B8-4CF8-84F7-AFA9849147B8@me.com>
To: Florian Rivoal <florian@rivoal.net>

> On Mar 22, 2016, at 5:34 PM, Florian Rivoal <florian@rivoal.net> wrote:
> 
> 
>> On Mar 23, 2016, at 01:56, aaron.www-style-@infinite-source.de wrote:
>> 
>> On 22.03.2016 08:45, Florian Rivoal wrote:
>>> 
>>>> On Mar 22, 2016, at 11:34, Rik Cabanier <cabanier@gmail.com> wrote:
>>>> 
>>>> It could be a new CSS property, for instance: compositing-space: "p3"/"sRGB"/"uncalibrated"/url(..)
>>> 
>>> Shouldn't that be "compositing space: sRGB | output | CIELab" ?
>>> 
>>> * sRGB: legacy "make everything dull" mode
>>> 
>>> * CIELab: because if you're compositing things coming form various color spaces or wide gamut color spaces, this is how you get the least color distortion. 
>>> 
>>> Say your sources are in a gamut wider than the output gamut, and you have semi-transparent very saturated red on top of very saturated blue. If you composite in CIELab, then convert to the output gamut, you'll get a not very saturated color that may not need clipping to fit the output gamut.
>>> 
>>> If you fit the colors to output gamut first, then do composition, the result will be different (and worse).
>>> 
>>> * output: because if all the things you are compositing do fit in the output device's gamut, doing composition directly in that space will be close enough to what you'd get using CIELab, but is computationally more efficient.
>> 
>> Compositing in the output gamut is not really close to compositing in
>> Lab. Try generating a saturated red-green gradient or rainbow in sRGB
>> and in Lab.
> 
> Right. I should have qualified that some more. Compositing in Lab gives
> better results, and compositing in the output gamut is sorta of close
> in some, but certainly not all scenarios. Depending on what you're
> doing, it may give be good enough, or maybe not.

The 4k/5k iMac and the new iPad Pro composite in unclipped sRGB, and map to the display colorspace (DCI-P3) at the end. We (WebKit) have no control over the colorspace used for compositing, so we donít have knobs to tune here.

Simon
Received on Wednesday, 23 March 2016 00:50:09 UTC

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