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colourability

v0.2.1

Published

Color-blindness and grayscale filters for any webpage via SVG feColorMatrix

Vulnerabilities

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Links

Git

Maintainers

mayukhroymayukhroy

Keywords

accessibilitycolor-blindnessdaltonizationsvgfilter

Readme

colourability

Test and improve color accessibility on real webpages with one tiny, zero-dependency TypeScript library.

colourability applies color transformations at the page level using a single SVG feColorMatrix, so it affects the entire DOM including Videos and Canvas elements.

Use it to:

  • simulate common color-vision deficiencies (protanopia, deuteranopia, tritanopia)
  • apply daltonization-style compensation matrices
  • tune strength live with intensity (0..1)
  • run custom 20-value matrices when needed

See it in action

The interactive demo applies the same filter to the whole page—images, <video>, <canvas>, and the rest of the DOM—so you can compare simulation and daltonization in context.

The recording lives next to the live demo in demo/. It is not included in the npm package (package.json "files"), so the published tarball stays small; GitHub renders it from the repository.

Install

npm install colourability

Usage

import Colourability from 'colourability';

const c11y = new Colourability();

// Simulate deuteranopia at full strength
c11y.apply('simulateColorBlindness/deuteranopia', { intensity: 1 });

// Tune effect strength while active
c11y.setIntensity(0.7);

// Remove filter and restore prior page state
colourability.remove();

Color-blindness workflows

1) Simulate what users may see


// Red-cone deficiency simulation
c11y.apply('simulateColorBlindness/protanopia');

// Green-cone deficiency simulation
c11y.apply('simulateColorBlindness/deuteranopia');

// Blue-cone deficiency simulation
c11y.apply('simulateColorBlindness/tritanopia');

2) Apply daltonization-style compensation


// Compensation preset (linear heuristic matrix)
c11y.apply('daltonizeColorBlindness/deuteranopia', { intensity: 1 });
c11y.setIntensity(0.85);

3) Compare quickly with a simple toggle


c11y.apply('simulateColorBlindness/deuteranopia');

// ... inspect UI ...

c11y.remove();

Built-in presets

Built-in ids use category/subname:

| Id | Purpose | |----|---------| | simulateColorBlindness/protanopia | Simulate red-cone (L) deficiency | | simulateColorBlindness/deuteranopia | Simulate green-cone (M) deficiency | | simulateColorBlindness/tritanopia | Simulate blue-cone (S) deficiency | | daltonizeColorBlindness/protanopia | Compensation heuristic (2I - M_sim) | | daltonizeColorBlindness/deuteranopia | Compensation heuristic (2I - M_sim) | | daltonizeColorBlindness/tritanopia | Compensation heuristic (2I - M_sim) | | visual/grayscale | BT.709 luminance grayscale | | fun/sepia | Stylized sepia | | fun/invert | Stylized invert |

intensity is always 0..1 and interpolates each matrix coefficient toward identity.

Custom matrix

Pass a 20-number feColorMatrix values string (row-major, same format as built-ins). For example, the identity (no-op) matrix:


const IDENTITY =
  '1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0';

c11y.applyMatrix(IDENTITY, { intensity: 0.5 });

API

  • apply(name, options?) — inject/update SVG filter and set filter: url(#__colourability-active__) on <html>
  • applyMatrix(matrix, options?) — same as apply, but with a raw 20-coefficient matrix string
  • remove() — remove SVG and restore the previous filter style
  • setIntensity(value) — adjust strength while a filter is active (preset or custom matrix)
  • list() — built-in preset ids
  • getState() — { active, customMatrix, options } — active is set for built-ins; customMatrix is set when applyMatrix was used

Why this approach works

A hidden <svg> in <head> defines <filter id="__colourability-active__"> with color-interpolation-filters="linearRGB". The root element then references it via CSS filter: url(#__colourability-active__).

This means:

  • one consistent mechanism for grayscale, simulation, and daltonization
  • no fullscreen overlay hacks
  • pointer events and interaction model stay natural

Browser script (IIFE / UMD)

After building, load dist/colourability.min.js and use the global Colourability constructor.

Versioning (0.x)

While the major version is 0, minor releases may include breaking API or preset-id changes. Pin the version range you need for production.

Contributing

See CONTRIBUTING.md.

License

MIT — see LICENSE.