ajstrand/a11y-contrast

A CLI utility to calculate/verify accessible magic numbers for a color palette.

A11y Contrast

A CLI utility to calculate/verify accessible magic numbers for a color palette. Read my blog post for some more information.

Installation

This tool requires Node.js version 12+.

Install globally:

$ yarn add -g a11y-contrast     # Yarn
$ npm install -g a11y-contrast  # Npm

Or install as a local dependency:

$ yarn add a11y-contrast            # Yarn
$ npm install --save a11y-contrast  # Npm

Or use without installing:

$ npx a11y-contrast <file>

Usage

View program help:

$ a11y-contrast --help
Usage: a11y-contrast <file> [options]

Arguments:
  <file>  Color palette file                              [required] [file]

Options:
  --min-ratio-3    Verify magic number for ratio 3                 [number]
  --min-ratio-4.5  Verify magic number for ratio 4.5               [number]
  --min-ratio-7    Verify magic number for ratio 7                 [number]
  -h, --help       Show help                     [commands: help] [boolean]
  -v, --version    Show version number        [commands: version] [boolean]

Run a full report for a color palette file:

$ a11y-contrast <file>

Verify that the color palette fulfills certain magic numbers per contrast ratio:

$ a11y-contrast <file> --min-ratio-3=40 --min-ratio-4.5=50 --min-ratio-7=70

Color palette format

This tool handles flat or nested JSON files with color grades between 0 and 100.

• Flat JSON:

{
  "blue-10": "#d9e8f6",
  "blue-20": "#aacdec",
  "blue-30": "#73b3e7",
  "green-10": "#dfeacd",
  "green-20": "#b8d293",
  "green-30": "#9bb672"
}

• Nested JSON:

{
  "blue": {
    "blue-10": "#d9e8f6",
    "blue-20": "#aacdec",
    "blue-30": "#73b3e7"
  },
  "green": {
    "green-10": "#dfeacd",
    "green-20": "#b8d293",
    "green-30": "#9bb672"
  }
}

Check out some example color palettes under /examples.

License

This project and its contents are open source under the MIT license.