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Re: [csswg-drafts] [mediaqueries-5] Draft text for in-gamut MQ, see #5045 (#5523)

From: Mike Bremford via GitHub <sysbot+gh@w3.org>
Date: Wed, 30 Sep 2020 08:50:26 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-701255666-1601455825-sysbot+gh@w3.org>
I can't speak for most of this, but you mentioned PDF and my ears started burning...

Generally I'd agree with Florian's statement that PDF can represent any color in any color-space, so would always return true here. There are specific situations where that might not be the case, but they're always going to be user-agent specific - for example, a PDF can be created with an "Output Intent" color-space, which describes the intended printing conditions for the PDF. This concept used with both PDF/A or PDF/X. Targeting a specific Output Intent is possible with several of the CSS to PDF engines.

It's possible you _might_ want to ensure all colors are within that color-space when you're generating the PDF, but this is a decision based on the intended use of the PDF by whoever is making it. It's not a hard requirement based on the file format.  Specifying an Output Intent is fairly common. Limiting colors to only be within that Output Intent is less common.

What's more common in PDF is disallowing a particular color-space entirely - for example, disallowing all RGB colors, or everything but CMYK. The "in-gamut" test wouldn't really help here; a media-query for this would need to look more like
`@media (colorspace:display-p3)`, so it could be used to select between RGB and CMYK bitmap images (for example). This query would be "can I accept content in this colorspace". However that's obviously a different issue to the one under discussion.

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