oklab 0.1.0

lightweight python implementation of Björn Ottosson's oklab colour space

lightweight python implementation of Björn Ottosson's oklab/oklch colour space.

i like oklab but there isnt a straightforward python package for working with it. so i made it.

install

install it from PyPI:

python -m pip install oklab

how to use?

import oklab

oklab.lch_to_hex((0.75, 0.125, 310.0))
# '#c697e9'

oklab.hex_to_lch('#ff0000')
# (0.6279536182521783, 0.25762679148825324, 29.227131291763712)

oklab.lab_to_xyz((1.0, 0.0, 0.0))
# (0.9504559270516719, 0.9999999999999998, 1.0890577507598782)

features

• 6 formats: rgb, hex, lab, lch, xyz, lms
• 30 conversion functions (complete graph)
• numerical accuracy + roundtrip precision
• source correctness
• zero dependencies
• clamping (in native oklab space via chroma reduction)
• configurable RGB primaries (P3, rec2020, …)
• [❌] CMYK support (scope creep)

sources

• function names inspired by hsluv
• outputs sanity-checked against oklch.com and wikipedia
• M0 sourced from Björn's CSSWG comment
• M2_inv sourced from Björn's blogpost
• XYZ_TO_RGB, RGB_TO_XYZ sourced from colour science
• M1, M1_inv, M2, RGB_TO_LMS, LMS_TO_RGB derived numerically using numpy
• tests sourced from Björn's blogpost

conversion graph

here is a graph of the atomic conversions:

• lab: oklab cartesian space
• lch: oklch cylindrical space
• lms: intermediate lms-like space
• xyz: CIEXYZ space
• rgb: sRGB
• hex: 8-bit sRGB in hexadecimal

all composed conversions are derived via shortest path in this graph