opticquiz-cvd 1.1.0

Color accessibility engine: colorblind-safety (protan/deutan/tritan, Machado 2009 + CIEDE2000), palette fixing, and WCAG contrast. Zero dependencies; drops into any matplotlib/plotly workflow.

opticquiz-cvd (Python)

Is your chart colorblind-safe? Red-green color-vision deficiency affects ~1 in 12 men — and the classic failure is a plot where the red series and the green series look identical to those readers. This checks any palette for that, with zero dependencies, and drops straight into a matplotlib / plotly / seaborn workflow.

It simulates protanopia, deuteranopia and tritanopia (Machado, Oliveira & Fernandes, 2009) and scores perceptual difference with CIEDE2000, flagging pairs that are clearly distinct to normal vision but collapse under a color-vision-deficiency simulation.

Method (citable): https://doi.org/10.5281/zenodo.21310578

Install

pip install opticquiz-cvd

Use it on a chart palette

import opticquiz_cvd as cvd

report = cvd.check_palette(["#d7191c", "#1a9641", "#2166ac"])
report["pass"]                         # False
report["types"]["deutan"]["conflicts"]
# [{'a': '#d7191c', 'b': '#1a9641', 'normal': 70.6, 'sim': 8.1, 'severity': 'risk'}]

Works directly with matplotlib colors (hex, names, or 0-1 RGB tuples):

import matplotlib.pyplot as plt, opticquiz_cvd as cvd
cycle = plt.rcParams["axes.prop_cycle"].by_key()["color"]
print("colorblind-safe:", cvd.check_palette(cycle)["pass"])

cvd.simulate((0.84, 0.10, 0.11), "deutan")   # '#8a7b0c'  (how a deuteranope sees it)
cvd.delta_e("#d7191c", "#1a9641")            # 70.6

Command line:

python -m opticquiz_cvd "#d7191c" "#1a9641" "#2166ac"
# FAIL - color conflicts found (3 colors)
#   deutan: #d7191c/#1a9641 dE8.1(risk)

Honest scope

Simulates a model of color-vision deficiency — an approximation of a diverse population, not any single person's vision — and results depend on an uncalibrated screen. It reliably catches classic red-green and blue-yellow conflicts. It is not a legal accessibility audit and does not certify ADA / Section 508 / WCAG / EU Accessibility Act compliance.

License

MIT. Method: Machado, Oliveira & Fernandes (2009) + CIEDE2000. Part of OpticQuiz.