cvdplate

Generate Ishihara-style pseudoisochromatic color-vision test plates. A digit is hidden in a field of colored dots so it reads to normal vision but collapses under protanopia, deuteranopia, or tritanopia. The JS companion to the ishihara Python package.

npm install cvdplate

const cvdplate = require("cvdplate");

const png = cvdplate.plate("7", { type: "deutan", size: 480, seed: 42 });
require("fs").writeFileSync("plate-7.png", png);   // a 7 that vanishes for deuteranopes

API

• plate(number, opts?) → a PNG Buffer.
  • number — the digit(s) to hide, e.g. "7" or "29" (0–9).
  • opts.type — "protan" | "deutan" | "tritan" (default "deutan").
  • opts.size — plate size in px (default 480).
  • opts.seed — integer; same seed → identical plate (default 1).
• pickPair(type) → { figure, background, normal, sim } — the color pair chosen for that deficiency, with its normal and simulated CIEDE2000 differences.

How the colors are chosen

The figure/background pair isn't guessed — it's searched with opticquiz-cvd's deltaE and simulate: a pair with a large normal CIEDE2000 difference and a small difference after simulating the target deficiency (Machado, Oliveira & Fernandes 2009). So the "hiding" is measured. Method, open access: https://doi.org/10.5281/zenodo.21310578

Not a clinical instrument

A demonstration/screening aid. On-screen color is not calibrated, so this is not a diagnostic Ishihara test. ishihara (Python) generates plates from a seed with no dependencies; this ports the idea to Node.

Licence

MIT.