charts.palette

export function palette(scheme: string, count: number, cycle: boolean): readonly string[]

import { palette } from "#fune/charts.palette@^1";

import { PALETTES } from "./charts_palette_data.ts";  ← this capability’s own data, compiled from data/palettes.json into the same file by fune build

/**
 * The first `count` colours of a named categorical scheme, in its order.
 *
 * A scheme has a fixed number of colours chosen to stay distinguishable to
 * people with colour-vision deficiencies; asking for more is an error unless
 * `cycle` says repeating them is acceptable, because a ninth series silently
 * reusing the first colour is a misleading chart.
 */
export function palette(scheme: string, count: number, cycle: boolean): readonly string[] {
  const colours = PALETTES.filter((c) => c.scheme === scheme)
    .slice()
    .sort((a, b) => a.position - b.position)
    .map((c) => c.hex);
  if (colours.length === 0) throw new RangeError(`unknown palette "${scheme}"; use okabe-ito or tol-bright`);
  if (!Number.isInteger(count) || count < 0) {
    throw new RangeError(`count must be a whole number of at least 0, received ${count}`);
  }
  if (count > colours.length && !cycle) {
    throw new RangeError(`palette "${scheme}" has only ${colours.length} colours; pass cycle to repeat them`);
  }
  const out: string[] = [];
  for (let i = 0; i < count; i++) out.push(colours[i % colours.length]);
  return out;
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and nothing else, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add charts.palette

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./charts.palette-1.0.0-typescript.fune, or fetch it from a terminal with fune pull charts.palette@1.0.0:typescript.

The whole function, every language, is one file too: charts.palette-1.0.0.fune, 10,984 bytes, sha256 ddf253584a9c2cad154b151e0ff42da0782096c9ab4744064ea04fc36c25b126. It installs into a project of any language.

// fune: before charts.palette

// fune: after charts.palette

// fune: step charts.palette after <n|label>

More from the author

The colours are data (`data/palettes.json`, one row per colour with its position and name), not code. They describe fixed published schemes rather than rules that change over time, so the file has no `effective` columns and is never pruned.

Asking for more colours than a scheme has is an error unless `cycle` is true: a ninth series quietly reusing the first colour makes two series look like one. With `cycle`, colours repeat from the start. All hex is lowercase `#rrggbb`.

Sources: M. Okabe and K. Ito, "Color Universal Design (CUD): How to make figures and presentations that are friendly to colorblind people" (2002, rev. 2008), https://jfly.uni-koeln.de/html/color_blind/ (RGB 0-255 values: black 0,0,0; orange 230,159,0; sky blue 86,180,233; bluish green 0,158,115; yellow 240,228,66; blue 0,114,178; vermillion 213,94,0; reddish purple 204,121,167); B. Wong, "Points of view: Color blindness", Nature Methods 8, 441 (2011); P. Tol, "Colour Schemes" (SRON technical note SRON/EPS/TN/09-002, 2021), https://sronpersonalpages.nl/~pault/ (bright: #4477AA, #EE6677, #228833, #CCBB44, #66CCEE, #AA3377, #BBBBBB).

Files