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color_cpal_brightness

Simon Cozens edited this page May 8, 2025 · 2 revisions

Color layers should have a minimum brightness.

color_cpal_brightness

  • Applies to: TTF
  • Fontspector can hotfix?: no
  • Fontspector can fix sources?: no

Rationale

Layers of a COLRv0 font should not be too dark or too bright. When layer colors are set explicitly, they can't be changed and they may turn out illegible against dark or bright backgrounds.

While traditional color-less fonts can be colored in design apps or CSS, a black color definition in a COLRv0 font actually means that that layer will be rendered in black regardless of the background color. This leads to text becoming invisible against a dark background, for instance when using a dark theme in a web browser or operating system.

This check ensures that layer colors are at least 10% bright and at most 90% bright, when not already set to the current color (0xFFFF).

Proposal

Profiles

  • universal (in section 'Universal Profile Checks')

  • googlefonts (in section 'Universal Profile Checks')

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