olfarve

Øl farve ("beer color") renders SRM and EBC beer color values as sRGB colors, following the spectral model described by A. J. de Lange, "Color," in Brewing Materials and Processes, Elsevier, 2016, pp. 199-249.

Given a color value and an optical path length (the width of the glass the beer is viewed through), the sample's spectral transmittance is derived from its absorption coefficient at 430 nm via the Beer-Lambert law, integrated against the CIE 1931 color matching functions of the 2 degree standard colorimetric observer under illuminant D65, and the resulting XYZ tristimulus values are transformed to sRGB.

Installation

npm install olfarve

The package requires Node.js 22.12 or newer and has no runtime dependencies. It ships both ESM and CommonJS builds along with TypeScript declarations.

Usage

import { srmToSrgb, ebcToSrgb, absorptionToSrgb } from 'olfarve';

srmToSrgb(10).toHex();
ebcToSrgb(20).toHex();

// The default path length is 5 cm, the width of a typical sample glass
srmToSrgb(10, 1.0).toHex();

// Results are SrgbColor instances of gamma encoded components in [0, 1]
const color = srmToSrgb(10);
color.r;
color.g;
color.b;
color.toRgb8();

// Or start from an absorbance measured at 430 nm
absorptionToSrgb(0.7874);

CommonJS works the same way:

const { srmToSrgb } = require('olfarve');

So does a plain HTML page, via jsDelivr:

<script type="module">
  import { srmToSrgb } from 'https://cdn.jsdelivr.net/npm/[email protected]/dist/index.mjs';
  document.body.style.background = srmToSrgb(10).toHex();
</script>

Command line

Installing the package provides an olfarve command. It takes one or more color values and prints them as CSV:

npx olfarve 1 2 10

1,#fae8b6
2,#f4d180
10,#ba5b00

Pick a scale and a path length:

npx olfarve --scale ebc --path-length 1.0 8 20 40

Run npx olfarve --help for the full list of options.

Development

npm install
npm run check