cvdsim

See a color, a palette, or a whole image the way a colorblind person does. Where cvdsafe judges whether colors are safe, cvdsim shows you — it recolors a hex, or an entire PNG/JPEG, as protanopia, deuteranopia, or tritanopia renders it.

npm install cvdsim

const dalton = require("cvdsim");

dalton.simulate("#d7191c", "deutan");   // "#8a7b0c" — that warning red, to a deuteranope
dalton.simulateAll("#1a9641");          // { protan: "#988839", deutan: "#8a7f48", tritan: "#009383" }

// Recolor a chart the way a red-green colorblind viewer sees it:
const png = dalton.simulateImage("./dashboard.png", "deutan");
require("fs").writeFileSync("./dashboard-deutan.png", png);

API

• simulate(color, type, severity?) → the color as one deficiency sees it, as hex. type is "protan", "deutan", or "tritan".
• simulateAll(color, severity?) → { protan, deutan, tritan } for one color at once.
• simulateImage(input, type, opts?) → a PNG Buffer of the image recolored. input is a file path, a Buffer, or a base64 data: URI; PNG and JPEG are read. opts.severity (0..1, default 1) sets strength; opts.maxSide caps the longest side (default 2000 px, 0 = original).

severity lets you show a partial deficiency (anomalous trichromacy), not only the full dichromat case — simulate("#d7191c", "deutan", 0.5) is a milder deuteranomaly.

How it works

cvdsim is a thin lens over opticquiz-cvd: every pixel's transform is that engine's simulate(), which uses the Machado, Oliveira & Fernandes (2009) deficiency matrices. The image path just decodes, runs each distinct color through the engine once via a lookup table, and re-encodes — there is no second copy of the colorimetry to drift, and no native image dependency to fail on install (pngjs + jpeg-js are pure JS). Method, open access: https://doi.org/10.5281/zenodo.21310578

Not a clinical tool

A simulation for design and communication — it approximates how deficient color vision renders an image. It is not a diagnosis, and no on-screen rendering is exact for a given individual.

Licence

MIT.