- From: Mark Watson <watsonm@netflix.com>
- Date: Tue, 20 Sep 2016 13:53:03 +0100
- To: Rik Cabanier <cabanier@gmail.com>
- Cc: Rossen Atanassov <Rossen.Atanassov@microsoft.com>, "www-style@w3.org" <www-style@w3.org>
- Message-ID: <CAEnTvdCtVWRC1-useA6ntJMDgu7HQr3NtfiV=u3LhppGV3wkew@mail.gmail.com>
On Tue, Sep 20, 2016 at 1:30 PM, Rik Cabanier <cabanier@gmail.com> wrote: > Hi Mark, > > I hope things were cleared up at the CSS meeting yesterday [1]. > > Here's the link to the iccMax specification: http://www. > color.org/iccmax.xalter > and the link to a reference implementation: https://github.com/ > InternationalColorConsortium/RefIccMAX > > For now, it doesn't look like any changes are need to the color spec. > I think the two things which came up specifically with the color specification were: (i) the predefined "dci-p3" profile is mis-named. There should be some changes to clarify that this is not DCI P3, but rather a profile defined in this specification which makes used of the DCI P3 color primaries. You could call it "web-p3" or "display-p3" or whetever. (ii) when the update to iccMax is done, it would be good to have at least one predefined profile for HDR (e.g. BT.2100 / PQ), especially since I heard at least one implementor say they did not intend to implement arbitrary ICC profiles, but rather just the predefined ones The question of where to map the SDR / sRGB luminance range when compositing with HDR is unsolved. It may be that for consistent results across platforms this needs to be specified. But there needs to be a period of experimentation on that before we could conclude either that specification is needed or that CSS color is a good place to specify it. ...Mark > Once iccMax is sorted out, it should simply refer to that. > > Rik > > 1: https://logs.csswg.org/irc.w3.org/css/2016-09-19/#e721928 > > On Mon, Sep 19, 2016 at 1:21 AM, Mark Watson <watsonm@netflix.com> wrote: > >> >> >> On Sep 18, 2016, at 10:36 PM, Rik Cabanier <cabanier@gmail.com> wrote: >> >> >> >> On Sun, Sep 18, 2016 at 10:19 PM, Mark Watson <watsonm@netflix.com> >> wrote: >> >>> >>> >>> On Sep 18, 2016, at 6:23 PM, Rik Cabanier <cabanier@gmail.com> wrote: >>> >>> >>> >>> On Sat, Sep 17, 2016 at 7:23 PM, Mark Watson <watsonm@netflix.com> >>> wrote: >>> >>>> >>>> >>>> On Fri, Sep 16, 2016 at 12:22 PM, Rik Cabanier <cabanier@gmail.com> >>>> wrote: >>>> >>>>> >>>>> >>>>> On Friday, September 16, 2016, Mark Watson <watsonm@netflix.com> >>>>> wrote: >>>>> >>>>>> >>>>>> >>>>>> On Fri, Sep 16, 2016 at 10:11 AM, Rik Cabanier <cabanier@gmail.com> >>>>>> wrote: >>>>>> >>>>>>> >>>>>>> >>>>>>> On Thu, Sep 15, 2016 at 12:22 PM, Rik Cabanier <cabanier@gmail.com> >>>>>>> wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Thu, Sep 15, 2016 at 11:57 AM, Mark Watson <watsonm@netflix.com> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Thu, Sep 15, 2016 at 11:25 AM, Rik Cabanier <cabanier@gmail.com >>>>>>>>> > wrote: >>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Thu, Sep 15, 2016 at 11:01 AM, Mark Watson < >>>>>>>>>> watsonm@netflix.com> wrote: >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> On Thu, Sep 15, 2016 at 10:41 AM, Rik Cabanier < >>>>>>>>>>> cabanier@gmail.com> wrote: >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> On Thu, Sep 15, 2016 at 10:21 AM, Mark Watson < >>>>>>>>>>>> watsonm@netflix.com> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> On Thu, Sep 15, 2016 at 9:58 AM, Rik Cabanier < >>>>>>>>>>>>> cabanier@gmail.com> wrote: >>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> On Thu, Sep 15, 2016 at 7:35 AM, Mark Watson < >>>>>>>>>>>>>> watsonm@netflix.com> wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>>> > On Sep 14, 2016, at 10:05 PM, Rossen Atanassov < >>>>>>>>>>>>>>> Rossen.Atanassov@microsoft.com> wrote: >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> >> On Wed, Sep 14, 2016 at 16:53:53, Mark Watson wrote: >>>>>>>>>>>>>>> >> >>>>>>>>>>>>>>> >> I have some use-cases and issues / questions related to >>>>>>>>>>>>>>> High Dynamic Range >>>>>>>>>>>>>>> >> graphics / images and how they could be supported in CSS. >>>>>>>>>>>>>>> I wondered if this >>>>>>>>>>>>>>> >> topic was or could be on the agenda for next week ? >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> > Are you referring to our TPAC agenda? If so, we don't have >>>>>>>>>>>>>>> the topic scheduled and looking through everything we have it is doubtful >>>>>>>>>>>>>>> we could get to it. >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> > Could you summarize your proposal? Is this something >>>>>>>>>>>>>>> proposed at WICG already? >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Yes, TPAC. I've raised the issue of HDR a few times on the >>>>>>>>>>>>>>> CSS list, >>>>>>>>>>>>>>> but with no real response. We had a breakout at TPAC last >>>>>>>>>>>>>>> year, but no >>>>>>>>>>>>>>> one from CSS attended. I imagine that is because people do >>>>>>>>>>>>>>> not yet >>>>>>>>>>>>>>> have real hardware / platform APIs with which to play with >>>>>>>>>>>>>>> this >>>>>>>>>>>>>>> functionality. Those will soon be available, so it seemed >>>>>>>>>>>>>>> good timing >>>>>>>>>>>>>>> to raise it again and explain the various problems. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> I only have problems, not a proposal. The basic problem (as I >>>>>>>>>>>>>>> understand it) is that with HDR displays, users are unlikely >>>>>>>>>>>>>>> to want >>>>>>>>>>>>>>> the peak white for regular sRGB to map to the peak luminance >>>>>>>>>>>>>>> of the >>>>>>>>>>>>>>> display. That would make desktops blindingly bright. So >>>>>>>>>>>>>>> there needs to >>>>>>>>>>>>>>> be a way for pages to signal when they are providing data in >>>>>>>>>>>>>>> the sRGB >>>>>>>>>>>>>>> luminance space (where peak white is what the user has set >>>>>>>>>>>>>>> as a >>>>>>>>>>>>>>> comfortable luminance for their desktop according to current >>>>>>>>>>>>>>> ambient >>>>>>>>>>>>>>> light) and when they are providing data in a different >>>>>>>>>>>>>>> luminance >>>>>>>>>>>>>>> space, where peak white is brighter (exactly how bright is >>>>>>>>>>>>>>> one of he >>>>>>>>>>>>>>> questions to be answered.) >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> This is defined in the CSS color spec [1]. If no profile is >>>>>>>>>>>>>> provided, peak white is peak sRGB white. >>>>>>>>>>>>>> The fact that you get blindingly white is a browser bug. (I >>>>>>>>>>>>>> believe only Safari does this right today) >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> I think there is a mis-understanding here and that is why I >>>>>>>>>>>>> think the issue deserves discussion. >>>>>>>>>>>>> >>>>>>>>>>>>> As far as I can tell, [1] is entirely about color gamut. >>>>>>>>>>>>> Whilst there are many ways to identify colors, the specification does not >>>>>>>>>>>>> seem to treat dynamic range. The section you reference regarding profiles, >>>>>>>>>>>>> says "Others are more human-friendly to write and understand, *and >>>>>>>>>>>>> are converted to an sRGB color by CSS*". >>>>>>>>>>>>> >>>>>>>>>>>>> sRGB peak white will appear at the brightness the user prefers >>>>>>>>>>>>> for their environment (because most of the graphics they see are sRGB and >>>>>>>>>>>>> they will adjust the brightness control on their display). >>>>>>>>>>>>> >>>>>>>>>>>>> My point is that for capable displays, it should be possible >>>>>>>>>>>>> to make graphics brighter than that. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Yes, you can by either providing an image with an embedded >>>>>>>>>>>> profile that has a higher gamut than sRGB, or by specifying a CSS color [1] >>>>>>>>>>>> with an HDR profile. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Could you give an example of how you would specify an HDR >>>>>>>>>>> profile with CSS ? For example, if I wanted some white text that was twice >>>>>>>>>>> as bright as sRGB(255,255,255) text ? I don't see that in the css-color >>>>>>>>>>> specification. >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Dean wrote a blog about this: https://webkit.org/blog/ >>>>>>>>>> 6682/improving-color-on-the-web/ >>>>>>>>>> >>>>>>>>> >>>>>>>>> This is great, but it is all about gamut alone. >>>>>>>>> >>>>>>>>> I don't know what profile is twice as bright as sRGB, but >>>>>>>>>> color(rec2020 255 255 255) would be brighter than rgb(255, 255, 255) >>>>>>>>>> >>>>>>>>> >>>>>>>>> Why would you think that ? >>>>>>>>> >>>>>>>>> In video, at least, the Rec.2020 color space is used for both SDR >>>>>>>>> and HDR, with a variety of transfer functions. I don't know if Rec.2020 >>>>>>>>> defines a default transfer function, but if it does it is likely a gamma >>>>>>>>> function like sRGB, which is scene-referred. >>>>>>>>> >>>>>>>>> Someone has to decide, or signal, how the luminance range of that >>>>>>>>> 2020 data relates to the luminance range of sRGB data. It's not implied by >>>>>>>>> the color profile alone. >>>>>>>>> >>>>>>>>> >>>>>>>>>> >>>>>>>>>>> Note that I am not talking about a wider gamut - that seems to >>>>>>>>>>> be well covered - but a different dynamic range (i.e. a larger color >>>>>>>>>>> volume, not just larger color gamut). >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> What do you mean by "color volume". Are you talking about higher >>>>>>>>>> bit depths for compositing? >>>>>>>>>> >>>>>>>>> >>>>>>>>> No, but higher bit depths are important too. >>>>>>>>> >>>>>>>>> As far as I can tell, CSS and ICC profiles deal with color gamut: >>>>>>>>> subspaces of the 2-dimensional CIE color space. A color in that space can >>>>>>>>> be described by two coordinates. >>>>>>>>> >>>>>>>> >>>>>>> This is incorrect. ICC profiles use 3 dimensions. Most charts show >>>>>>> color spaces as 2D projections which is probably why you think this. >>>>>>> >>>>>>> >>>>>>>> An actual pixel color has 3 coordinates and resides in a *color >>>>>>>>> volume*: a three-dimensional space where the intersection of this >>>>>>>>> space and a plane is the CIE space. >>>>>>>>> >>>>>>>> >>>>>>> Color volume is part of ICC. >>>>>>> >>>>>>> >>>>>>>> The problem we have can be thought of as a backwards compatibilty >>>>>>>>> one. You *could* specify luminance on the same scale for all >>>>>>>>> image / graphics data sources. And, indeed, I expect this is what the >>>>>>>>> graphics plane APIs of all devices will look like. In that case an RGB >>>>>>>>> pixel in any color space with linear values ( 1.0, 1.0, 1.0 ) will be >>>>>>>>> rendered display peak luminance (or close). I believe this is the case with >>>>>>>>> CSS as things stand. >>>>>>>>> >>>>>>>> >>>>>>> According to the spec, rgb(255,255,255) is rendered on as peak sRGB >>>>>>> luminance which isn't necessarily the peak of what your devices is capable >>>>>>> of. >>>>>>> This is why you can now specify a profile (which controls the >>>>>>> brightness) so you can attain what your display is capable of. >>>>>>> >>>>>>> >>>>>>>> This would support any and all HDR images / graphics, but the >>>>>>>>> problem would be that peak white in both SDR and HDR data would be rendered >>>>>>>>> the same. Most importantly, peak white in desktop graphics would be the >>>>>>>>> same as specular highlights in HDR images. >>>>>>>>> >>>>>>>> >>>>>>> No since peak white is controlled by the ICC profile. >>>>>>> >>>>>>> >>>>>>>> Since most desktop applications are going to stay sRGB, we need >>>>>>>>> some new way for authors to specify pixels that are brighter than that. >>>>>>>>> >>>>>>>> >>>>>>> Why do you think that desktop apps are staying in sRGB? Most >>>>>>> graphics applications support ICC today and the good ones support HDR. >>>>>>> >>>>>>> >>>>>>>> >>>>>>>>>> >>>>>>>>>>> Those colors are then mapped to the "device" color which usually >>>>>>>>>>>> is the monitor's colorspace. If you have an HDR monitor and specify an HDR >>>>>>>>>>>> image, you will get colors that are brighter than sRGB white. >>>>>>>>>>>> >>>>>>>>>>>> Safari is already doing this for images so you can try this for >>>>>>>>>>>> yourself if you have a capable device. >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>>> If you do provide a profile, it will be used to map to the >>>>>>>>>>>>>> display. >>>>>>>>>>>>>> Is there a way to embed a profile in a video stream? >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Here I am not talking about video. But, yes, video metadata >>>>>>>>>>>>> specifies not only color gamut (primaries) but a transfer function which is >>>>>>>>>>>>> used to map between encoded luminance and actual luminance and is different >>>>>>>>>>>>> for HDR and SDR video. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> I think we need to specify what is done with video. It seems >>>>>>>>>>>> that this information needs to be used so the browser knows how to manage >>>>>>>>>>>> the video's colors. >>>>>>>>>>>> what happens today with video? >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Well, this is all rather new, so I doubt there is any >>>>>>>>>>> consistency. On the various devices we have seen which composite sRGB >>>>>>>>>>> graphics with HDR video it's highly variable. I expect when we see this on >>>>>>>>>>> devices with desktop-class browsers, the operating system will have made >>>>>>>>>>> some decision as to what luminance to map sRGB to, relative to the HDR >>>>>>>>>>> images. I've heard 80 nits. I've also heard of people planning to map sRGB >>>>>>>>>>> peak white to panel peak white. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> To obtain CSS use-cases, imagine first a still image extracted >>>>>>>>>>>>> from an HDR video, encoded in some still image format which carries HDR >>>>>>>>>>>>> metadata and which is supported by the browser. >>>>>>>>>>>>> >>>>>>>>>>>>> It should be possible to specify in CSS any color+luminance >>>>>>>>>>>>> that appears in that image. If the video or still image pixels are >>>>>>>>>>>>> constrained to be no brighter than the sRGB peak white (the luminance the >>>>>>>>>>>>> user prefers for their desktop), then you will not get any improvement in >>>>>>>>>>>>> appearance: for example specular highlights in the video / image would be >>>>>>>>>>>>> no brighter than for an SDR video / image, even though the display may be >>>>>>>>>>>>> capable of that. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Yes, extract the transfer function and other information from >>>>>>>>>>>> the video stream and use it to construct a profile. Then embed that profile >>>>>>>>>>>> in your still image. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> What about actually specifying one of those colors in CSS ? So >>>>>>>>>>> that I can have text or graphics matching the colors in the image ? >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> You can place the profile on your web server,load it with css >>>>>>>>>> using @color-profile and use the name with the css color property. >>>>>>>>>> >>>>>>>>> >>>>>>>>> Like I said, I don't think the profile is enough, since it is >>>>>>>>> addressing gamut. Certainly, Rec. 2020, for example, does not tell me how >>>>>>>>> much brighter than sRGB it's peak white should be. In video we have >>>>>>>>> additional metadata for that. >>>>>>>>> >>>>>>>> >>>>>>>> It seems that there are some differences between the video and >>>>>>>> desktop world. >>>>>>>> I'm going to talk to some of our color experts to learn more about >>>>>>>> this subject. >>>>>>>> >>>>>>> >>>>>>> I talked to our people that deal with color for our video >>>>>>> application (premiere and after effects) and they say there's no difference >>>>>>> between video and desktop profiles. >>>>>>> >>>>>> >>>>>> In video, signals are accompanied with data including, separately, >>>>>> the color gamut and the transfer function. If I look at BT.2020, for >>>>>> example, it specifies color primaries and a scene-referred transfer >>>>>> function mapping the quantized tristimulus values to linear in the range >>>>>> 0-1. BT.2020 does not tell you "how bright" (1,1,1) should be. >>>>>> >>>>>> It does say: >>>>>> >>>>>> "In typical production practice the encoding function of image >>>>>> sources is adjusted so that the final picture has the desired look, as >>>>>> viewed on a reference monitor having the reference decoding function of >>>>>> Recommendation ITU-R BT.1886, in the reference viewing environment defined >>>>>> in Recommendation ITU-R BT.2035." >>>>>> >>>>>> and BT.1886 specifies a peak luminance of 100 nits (the standard for >>>>>> SDR TV). >>>>>> >>>>>> For HDR video, we use the BT.2020 color gamut (primaries), with the >>>>>> SMPTE ST.2084 Transfer Function (PQ) which specifies mapping from quantized >>>>>> tristimulus values to absolute luminance (from 0 to 10,000nits). >>>>>> >>>>>> So, I still have the problem that specifying "rec2020" or "dci-p3" in >>>>>> CSS does not tell me how the luminance of those pixel values should be >>>>>> rendered relative to the luminance of "srgb". Indeed, if I look at Section >>>>>> 10.2, it specifies the mappings associated with these color spaces to a >>>>>> linear [ 0, 1 ] space. A natural assumption is that all three have the same >>>>>> peak luminance (whatever you map 1.0 to, determined by the brightness >>>>>> control on the display). >>>>>> >>>>>> I do see that ICC profiles can include a luminanceTag field, >>>>>> specifying "absolute luminance of emissive devices in candelas per square >>>>>> metre as described by the Y channel". So perhaps what I am looking for is a >>>>>> variant of the "rec2020" profile with this luminanceTag set to 10,000 and >>>>>> somehow specifying the PQ transfer function instead of the one in BT.2020. >>>>>> >>>>>> >>>>>> >>>>> I'm unsure about the video case. For images and artwork, all the >>>>> information you need should be covered by the ICC workflow. >>>>> >>>>> If you want, I can put you in touch with one of our color experts >>>>> since they are more familiar with the details. >>>>> >>>> >>>> Yes, that would be great, thanks. But I would also like an opportunity >>>> to discuss the problem with the wider CSS group. At a minimum, even if >>>> profiles solve this, the specification is unclear as to what the rec2020 >>>> profile refers to, since the 2020 colorspace is used for both SDR and HDR >>>> in video. >>>> >>> >>> I got a reply from our color people: >>> >>> [snip] >>> >>> iMac now supports HDR, with a peak of 500 nits. >>> >>> Classic SDR content is not mapped to 500 nits. >>> Instead it maps to a brightness set by the user, often around 200 nits. >>> Classic SDR content includes all legacy apps, such as Safari, MS Word, >>> email… >>> For these apps, MacOS maps their diffuse white (1.0, 255 etc) to this >>> 200 nit setting. >>> >>> In order to display HDR content above 200 nits, an app must produce >>> frame buffer values > 1.0. >>> Classic apps don’t know how to do that. >>> >>> HDR aware apps know that the peak of all non-HDR color spaces (sRGB, >>> BT.2020…) should be mapped to 1.0, which OS maps to 200 nits. >>> And for HDR spaces, they know that the diffuse white point in the HDR >>> space is also mapped to 1.0. >>> The diffuse white point for PQ-encoding is at 100-200 nits, not max code >>> value. >>> AFAIK both Apple and Msft maps PQ for 100 nits to diffuse white. >>> >>> If you want something brighter than sRGB white, then use a proper HDR >>> color space. >>> BT.2020 is not an HDR space. >>> HDR10 is an HDR space, with same primaries as BT.2020. >>> >>> >>> If you combine this with Simon Fraser's email: >>> >>> Compositing happens in 10-bit or half-float textures which may contain < >>> 0 or > 1 values. A P3 image is mapped into this unclipped sRGB space for >>> compositing, then the final result is mapped into Display-P3 at the end. >>> >>> then it looks that if you can tag something with HDR10 and the color >>> values are high enough, the result will be brighter than than 200 nits at >>> least on system that support HDR. (The unclipped sRGB space does sound a >>> bit weird.) >>> >>>> >>>> >>>>> I just use profiles as a black box. 😀 >>>>> >>>> >>>> The full power of iCC profiles may solve this. But what seems unclear >>>> to me is whether the profiles defined in CSS (sRGB, rec2020, dci-p3) are >>>> well enough defined for it to be clear how their luminance ranges should be >>>> mapped to actual physical luminance, *relative to each other*. >>>> >>>> For example, whilst sRGB, at least as defined in [1], defines peak >>>> white to be 80nits, BT.2020 (as I noted above) does not specify a peak >>>> luminance and at least with video is used with different transfer functions >>>> with peak luminance 100nits (SDR) or 10,000nits (HDR with PQ). So, what >>>> does it mean when you specify rec2020 in CSS ? And, if it means 100nits, >>>> because 2020 notes that this is a "typical" usage, how do I specify a >>>> profile where 2020 colorspace is used with 10,000nits peak ? Do >>>> implementations *actually* map the 2020 luminance range to 125% of the >>>> sRGB range and is that even the right thing to do ? >>>> >>>> (and this is before we even start talking about how video metadata can >>>> influence tone mapping and how one might be able to get the same tone >>>> mapping applied to graphics / images). >>>> >>>> If there is not time on the CSS agenda (which is see is rather full) >>>> for this, I wonder if there would be interest in a break-out session on >>>> Wednesday ? >>>> >>> >>> We could. The hard part would be to track down the experts. It's easy to >>> get confused by all the different color standards. >>> Your questions seem more about quality of implementation than the w3c >>> color specification. >>> >>> >>> I think your answer above demonstrates that there is a spec issue, not >>> just quality-of-implementation issues, since it is by no means clear from >>> the specification that the approach taken by Apple is the only one. >>> >> >> Currently, the spec chooses not to specify how a document should be >> rendered. This could be added once implementations and other specs (such as >> ICC) progress. >> >> However, if you follow the proposed color spec and tag everything the way >> you'd like it to render, the ICC conversions will give you the best output >> per the current output device. >> >> >> I think it's still under specified, as I explained above. Specifically >> the relative luminance of SDR and HDR color spaces as well as the issue >> below which you seem to agree with. >> >> >> >> >>> The approach described above - where the value 1.0 always means the same >>> thing independent of color space, seems reasonable, but also it would be >>> reasonable that if a color is tagged as being from an HDR space that the >>> peak white of that space is also 1.0. >>> >> >> Yes, that would be nice. >> >> >>> The question of what luminance value in an HDR space should be mapped to >>> the same as sRGB diffuse white (the 1.0 value) is not answered in the HDR >>> specifications I am aware of. >>> >>> Also, it would be nice to have a shorthand for 2020 color primaries used >>> with an HDR transfer function, for example as defined in BT.2100 with PQ. >>> >> >> These 3 issues are about HDR ICC profiles; not with the CSS color spec or >> anything that is controlled by w3c. >> >> >> I disagree. The first issue is relevant wherever you have compositing of >> data specified in multiple color spaces, SDR and HDR. The relative >> luminance mapping needs to be defined somewhere and I would expect each >> environment where this can happen to do so (and CSS is one such >> environment). >> >> The other issue is a straightforward request for CSS to define a >> shorthand for a specific HDR color space, as has been done for sRGB and >> 2020 in the color spec. This is certainly in scope. >> >> Maybe you should take this up with that organization? >> >> >> >>> These issues at least deserve discussion. >>> >> >> Yes. Let's have a meeting on Wednesday morning. Leonard is familiar with >> this ares and agreed to attend. >> >> >>> >>>> [1] https://www.w3.org/Graphics/Color/srgb >>>> >>>> >>>> >>>>> >>>>> If more is needed than what is already specked, we can bring it back >>>>> to the list. >>>>> >>>>>> >>>>>> >>>>>> >>>>>>> >>>>>>> >>>>>>>> I will be at TPAC next week as well so maybe we can have a short >>>>>>>> get-together. >>>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>>> If the WICG is the appropriate place to raise these >>>>>>>>>>>>>>> problems, I can do >>>>>>>>>>>>>>> that, but the experts are in CSS WG so I wondered if there >>>>>>>>>>>>>>> was >>>>>>>>>>>>>>> interest in learning about these issues. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Thanks ... Mark >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> 1: https://drafts.csswg.org/css-color/#color-type >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>> 1: https://drafts.csswg.org/css-color/#icc-colors >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>> 1: https://drafts.csswg.org/css-color/#at-profile >>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>> >>> >> >
Received on Tuesday, 20 September 2016 12:53:36 UTC