CSS Relative Alpha Colors

[CGQAQ]

Specification

https://drafts.csswg.org/css-color-5/#relative-alpha

Description

Relative alpha colors refer to an origin color, and only change the alpha channel. The meaning of alpha channels is defined in CSS Color 4 § 4.2 Representing Transparency in Colors: the syntax.

Documentation

https://bsky.app/profile/nerdy.dev/post/3mmsrchlp6k2o
mozilla/standards-positions#1396 (comment)

Browser support

https://chromestatus.com/feature/5070160203481088

[CGQAQ]

This is an issue create from #3864

cc @ddbeck

[ddbeck]

Thanks, @CGQAQ. I'm taking some notes here to help create a new feature entry YAML file. While it's not required, you review of the following would be welcome.

Name and ID

The ID is probably alpha. The name is likely to be "alpha()" or "Relative alpha colors".

Description

Our style emphasizes the feature's entry point, here a CSS function. So we'd probably describe as something like:

The alpha() CSS function computes a color value by adjusting the opacity of an origin color.

Compat data

This will probably have a single mdn/browser-compat-data key, css.types.color.alpha.

Support context

This appears to be shipping first in Chrome 150. Since this is not shipping yet, I'm labeling this as an early feature (though that will be short lived).

In addition to the Chrome status entry, I found the following noteworthy vendor URLs:

• Relative Alpha Colors mozilla/standards-positions#1396
• Relative Alpha Colors WebKit/standards-positions#657
• Firefox bug 2042646
• WebKit bug 315952

[CGQAQ]

LGTM, thanks for your work!

NOTE: We are very close to the end of the M150 shipping window; it may ship in M151 if we can not make it.