- From: Jeff Gilbert <jgilbert@mozilla.com>
- Date: Thu, 17 Jun 2021 16:52:00 -0700
- To: Pierre-Anthony Lemieux <pal@sandflow.com>
- Cc: Lars Borg <borg@adobe.com>, Chris Lilley <chris@w3.org>, "public-colorweb@w3.org" <public-colorweb@w3.org>
Yes, please! On Thu, Jun 17, 2021 at 4:25 PM Pierre-Anthony Lemieux <pal@sandflow.com> wrote: > > Hi Jeff et al., > > I see two complementary objectives: > > - specify mathematical expressions exactly, e.g. 4/3*pi*r^3, so that > the can be computed to arbitrary precision > - provide worked examples at a common precision, e.g. 4.188790205*r^3 > at 10 significant figures for float computation, so that interop can > be achieved > > Makes sense? > > Best, > > -- Pierre > > On Thu, Jun 17, 2021 at 3:49 PM Jeff Gilbert <jgilbert@mozilla.com> wrote: > > > > I can't speak for others, but I don't want very precise *results* of > > calculations per se, but rather I prefer to know the calculation > > methods themselves, and their precise inputs. It's difficult to reason > > about results without a clear path for how we got there. > > > > Eventually I do need the numbers to calculate with, but I got tired of > > trying to figure out if matrices I found in documentation were right > > for my particular usecases, and made this: > > https://jdashg.github.io/misc/colors/from-coeffs.html (the > > calculations are fairly legible in the JS source) > > > > Ideally we can give names to constructs, instead of, for example, "use > > the following very precise matrix given to 10 sig-figs...". If there's > > a constant that's 18.0/19.0, it's nice to know that, and not just see > > 0.9473684210526315. > > > > I've found this to be a huge ongoing problem and source of confusion > > in colorspace work, but that naming things and showing-my-work goes a > > long way to helping. > > > > On Thu, Jun 17, 2021 at 3:30 PM Pierre-Anthony Lemieux <pal@sandflow.com> wrote: > > > > > > > Please, no long numbers! > > > > > > I do not understand this blanket statement. > > > > > > The accuracy of individual constants within an expression should be > > > sufficient to achieve the desired accuracy for the entire expression. > > > > > > For example, it would make no sense to specify π = 3.14 in f(x) = π·d > > > if f(x) is intended to compute the circumference of a circle to an > > > accuracy of ±0.00001. > > > > > > > > > > > > > > > On Thu, Jun 17, 2021 at 2:39 PM Lars Borg <borg@adobe.com> wrote: > > > > > > > > Please, no long numbers! > > > > > > > > And I’m not alone on this. > > > > > > > > > > > > > > > > Lars > > > > > > > > > > > > > > > > From: Chris Lilley <chris@w3.org> > > > > Date: Thursday, June 17, 2021 at 3:00 AM > > > > To: "public-colorweb@w3.org" <public-colorweb@w3.org> > > > > Subject: Re: Conversions for HDR Canvas Specification > > > > Resent-From: <public-colorweb@w3.org> > > > > Resent-Date: Thursday, June 17, 2021 at 3:00 AM > > > > > > > > > > > > > > > > > > > > > > > > On 2021-06-16 11:53, Simon Thompson - NM wrote: > > > > > > > > Hi all, > > > > > > > > > > > > > > > > I’ve added a list of suggested colour forward and reverse transforms between extended-sRGB, extended-linear-sRGB and bt2100-hlg and a suggested simple tone-mapping for displaying bt2100-hlg on an sRGB display to issue #50 - https://github.com/w3c/ColorWeb-CG/issues/50. I’ve tried to follow the style of the example in TTMLv2 provided by Pierre. > > > > > > > > > > > > > > > > I can recalculate the matrices to a different number of significant figures if necessary – is there a consensus on accuracy levels for web operations? > > > > > > > > In general, since "space of the printed publication"is no longer a concern, I prefer to list to full precision. > > > > > > > > I have seen several problems arising from round-off errors and round-tripping, so there is no good reason to round off. > > > > > > > > > > > > > > > > Would Dolby colleagues be able to add the bt2100-pq versions to the list? There is a PQ example in Pierre’s TTMLv2 link. > > > > > > > > > > > > > > > > Best Regards > > > > > > > > > > > > > > > > Simon > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Simon Thompson > > > > Senior R&D Engineer > > > > > > > > > > > > > > > > -- > > > > > > > > Chris Lilley > > > > > > > > @svgeesus > > > > > > > > Technical Director @ W3C > > > > > > > > W3C Strategy Team, Core Web Design > > > > > > > > W3C Architecture & Technology Team, Core Web & Media > > >
Received on Thursday, 17 June 2021 23:53:21 UTC