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Re: [csswg-drafts] [css-color] interpolating between color spaces

From: CSS Meeting Bot via GitHub <sysbot+gh@w3.org>
Date: Fri, 21 Apr 2017 03:08:47 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-296034013-1492744125-sysbot+gh@w3.org>
The CSS Working Group just discussed `Interpolation between different color spaces`, and agreed to the following resolutions:

* `RESOLVED: Use the working color space for now.`

<details><summary>The full IRC log of that discussion</summary>

```
<dino> Topic: Interpolation between different color spaces
<dino> Github Topic: https://github.com/w3c/csswg-drafts/issues/883
<flackr> dino: following on from issue 300, if experimentation pans out than I agree with ChrisL_, do interpolation in document color space which means you may get discontinuities at the ends
<flackr> ChrisL_: you said earlier you wouldn't get discontinuities at the end
<flackr> dino: I said if experimentation works out, then hopefully the working color space does something that does not result in discontinuities
<flackr> Rossen: we can independently resolve on interpolating
<dino> linear-gradient(rgb(255, 0, 0), color(display-p3 1))
<flackr> dino: this will get a solid color, not a gradient in the working color space SRGB
<flackr> leaverou: if the working space is SRGB, then the display color is clipped?
<flackr> dino: it's clipped within a gradient, but not in the background color
<flackr> dino: I'm trying to come up with a color space that's the same as what people are used to but allows interpolation outside of it
<flackr> ChrisL_: explains something
<leaverou> leaverou: We can't we interpolate in the union of the two working spaces or lab? The author intent is clear: I want to interpolate between sRGB red and P3 red. Those are not the same colours.
<leaverou> s/We can't we/Why can't we/
<ChrisL_> chrisl: this is why the working colorspace exists. its npt possible to pick the 'larger' because they can intersect. for example p3 and adobergb
<ChrisL_> this is why we have working colorspace which can be set to Rec2020, or XYZ, or Lab
<ChrisL_> and will never clip
<ChrisL_> This is why I want to have lab as an option because apart from not clipping it also gives better results
<leaverou> http://dabblet.com/gist/1b1344c158bf599bfc1ad47cc1265e7a
<flackr> dino: I don't know how expensive it is to use Lab
<flackr> ChrisL_: when you have two things with different color profiles they'll get converted to XYZ or Lab
<ChrisL_> because those are the two profile connection spaces for ICC profiles
<flackr> dino: I will provide feedback based on our implementation. We can always use Lab and this issue will go away - get no banding
<flackr> dino: at which point you asked why do we need a working color space for the document?
<flackr> leaverou: we still need to define what colors in the document resolve to
<flackr> dbaron: when you're combining different stylesheets from multiple sources you don't want one stylesheet to change the meaning of things in another stylesheet
<flackr> ??: variables?
<flackr> dbaron: you know you're doing it
<flackr> TabAtkins: we previously had issues where we didn't want to let other unrelated stylesheets mess with your colors
<leaverou> s/we still need to define what colors in the document resolve to/we still need to define what the rgb(), hsl() etc colors in the document resolve to/
<flackr> dino: if an imported stylesheet sets the document working color space we should come up with some rules for how its processed
<flackr> TabAtkins: let's give colors all defined meanings
<flackr> ChrisL_: let's continue to, they've always had defined meanings but the fidelity has ramped up
<flackr> leaverou: if all colors have defined meanings, why do we need a working color space?
<ChrisL_> continue to, as has been fdefined since css1
<flackr> dino: we only need a working color space for interpolation
<flackr> dbaron: even if color A is defined and color B is defined, it depends on the color space what is half-way between them
<flackr> leaverou: convert to Lab
<flackr> TabAtkins: converting to Lab is *an* answer, not necessarily the answer
<flackr> ChrisL_: that's an option, it's not compatible with what we have at the moment
<flackr> leaverou: to be better
<flackr> dbaron: but it would be a change
<dbaron> s/depends on the color space/depends on the working color space/
<flackr> Rossen: do we have a counter proposal? if not let's go with dino's proposal
<flackr> Rossen: you'd interpolate between colors in the document working space
<flackr> RESOLVED: Use the working color space for now.
<TabAtkins> ScribeNick: TabAtkins
<ChrisL_> s/Use the/Interpolate bweteen colors by converting them to the/
```
</details>


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Received on Friday, 21 April 2017 03:08:58 UTC

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