Re: [css-color] wider/deeper colors

On Tue, Mar 22, 2016 at 5:49 PM, Simon Fraser <smfr@me.com> wrote:

>
> > 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 don’t have knobs to tune
> here.


Why can't you use colorsync?
https://developer.apple.com/library/ios/technotes/tn2313/_index.html#//apple_ref/doc/uid/DTS40014694-CH1-FRAMEWORKS_FOR_COLOR_MATCHING_WHEN_RENDERING_TO_THE_DISPLAY
<https://developer.apple.com/library/ios/technotes/tn2313/_index.html#//apple_ref/doc/uid/DTS40014694-CH1-FRAMEWORKS_FOR_COLOR_MATCHING_WHEN_RENDERING_TO_THE_DISPLAY>

Also, if you composite in unclipped sRGB, how are you honoring images with
a high gamut profile such as p3 or AdobeRGB?