pyolfarve

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

pip install olfarve

Usage

import olfarve

olfarve.srm_to_srgb(10).to_hex()
olfarve.ebc_to_srgb(20).to_hex()

# The default path length is 5 cm, the width of a typical sample glass
olfarve.srm_to_srgb(10, path_length_cm=1.0).to_hex()

# Results are SRGBColor named tuples of gamma encoded components in [0, 1]
color = olfarve.srm_to_srgb(10)
color.r, color.g, color.b
color.to_rgb8()

# Or start from an absorbance measured at 430 nm
olfarve.absorption_to_srgb(0.7874)

Command line

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

olfarve 1 2 10

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

Pick a scale and a path length:

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

Run olfarve --help for the full list of options. The module is also executable via python -m olfarve.

Development

python -m venv .venv && . .venv/bin/activate
pip install -e . --group dev
pytest
ruff check .
mypy