W3C home > Mailing lists > Public > public-html@w3.org > March 2010

Re: Color Management in HTML5?

From: Maciej Stachowiak <mjs@apple.com>
Date: Sat, 06 Mar 2010 17:30:33 -0800
Cc: "L. David Baron" <dbaron@dbaron.org>, "public-html@w3.org" <public-html@w3.org>
Message-id: <EB7BFCB4-3698-4001-A52B-E5F2EC17DE43@apple.com>
To: Leonard Rosenthol <lrosenth@adobe.com>

On Mar 6, 2010, at 5:29 AM, Leonard Rosenthol wrote:

> And this discussion is EXACTLY why the ICC wants to get involved.
>
> As has been stated many times, the HTML5 spec is not only about the  
> language & grammar BUT is also a set of requirements for UAs to  
> ensure that all browsers render the same page in the same way.  As  
> such, that includes not only that the right image goes in the right  
> place on the page BUT that its colors are correct and match the  
> colors shown in other browsers.

Nonetheless, most color management issues are not HTML issues. They  
are mostly an issue for CSS. I would say the most fruitful avenue for  
the ICC would be to coordinate with the CSS WG.

>
> To accomplish this will mean that rules for color management within  
> a browser need to be stipulated in the standard itself.   For  
> example, the following (non-complete) list of questions need to  
> answered…
> ·         What is the “default colorspace”?

This is not an HTML issue. It's an issue for individual specs that  
deal with color. Typically, W3C and other specs seem to agree that the  
default colorspace is sRGB, though that is generally not implemented  
(except perhaps on Windows where it's typical to assume that device  
color is approximately sRGB.)

> ·         How to handle embedded profiles in images (and possibly  
> even how to look for them)

This is an issue for image format specs, or perhaps for a spec about  
how images should work on the Web.

> ·         How to handle CSS colors

That's an issue for the CSS spec.

> ·         How to handle SVG colors (which extend CSS a bit)

That's an issue for the SVG spec to the extent that it does not just  
defer to CSS.

> ·         Does Canvas need to be extended to deal with richer color  
> (ala SVG)?

My interpretation would be that Canvas uses CSS colors and therefore  
should follow CSS rules about color. If the spec doesn't clearly say  
that, then that's a bug.

> ·         Does video need to be extended?
>
> Would the correct process forward then be for the ICC to draft one  
> or more formal & comprehensive Change Proposals (which will most  
> likely be fairly widespread throughout one or more of the documents  
> currently being authored)?

The correct first step to request a spec change for HTML5 would be to  
file a bug. A Change Proposal would be out of order.

In all fairness I should warn you that it's likely the bug would be  
rejected as out of scope for HTML.

>
> Is it possible that some form of decision could be made to determine  
> the “feelings” of the committee ahead of time?  I would hate to  
> recommend to someone at the ICC that they invest the (huge) time  
> necessary to draft such a document , only then to have it not  
> approved.  Is there some sort of “pre-vote” or something that could  
> be used in this case?

Even without a "pre-vote", a Change Proposal would be out of order  
without following the earlier steps in the process. And in any case,  
probably the best venue to make proposals would be the CSS WG, not the  
HTML WG.

Regards,
Maciej

>
> Leonard
>
> From: Maciej Stachowiak [mailto:mjs@apple.com]
> Sent: Saturday, March 06, 2010 7:15 AM
> To: L. David Baron
> Cc: Leonard Rosenthol; public-html@w3.org
> Subject: Re: Color Management in HTML5?
>
>
> On Mar 5, 2010, at 2:04 PM, L. David Baron wrote:
>
>
> On Friday 2010-03-05 00:08 -0800, Maciej Stachowiak wrote:
>
> Just to report on what Safari does: we colormatch images that are
> tagged with an explicit colorspace, but we treat CSS colors and
> colors in untagged images as being in the device color space
> (instead of treating as sRGB). This seems to give a good balance
> between performance for the common case and color-correctness for
> cases where precise color is desired.
>
> Gecko does this too (I think starting in Firefox 3.5?), but we got
> quite a few complaints about it, and I'd like to change it.
>
> It has the significant disadvantage that the relationships between
> colors in different parts of the same page can be different
> depending on the device (when a page has both tagged images and
> other colors).
>
> I think we should move towards treating CSS colors (and untagged
> images) as sRGB, as CSS1, CSS2.1, and css3-color require.
>
> Long-term, we would like to do this in Safari (treat CSS colors and  
> untagged images as sRGB). In our attempts so far, there have been  
> two blockers:
>
> 1) Our attempts to do this so far have resulted in significant  
> performance regressions. We're still working on a way to do this  
> with good enough performance.
>
> 2) We have no way to get plugins to participate in colormatching. We  
> need additions to NPAPI to tell plugins whether to use device color  
> or sRGB, and we need plugins to adopt them. This is especially  
> critical for Adobe Flash, since there are pages that try to match  
> static background colors or background images to Flash. We've had  
> some discussions on this.
>
> Regards,
> Maciej
>
Received on Sunday, 7 March 2010 01:31:08 UTC

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