@alphatype/alda-js

Parser and utilities for the Alda skeleton motion font format.

Install

npm install @alphatype/alda-js

Or use via CDN (no install needed):

<script src="https://cdn.jsdelivr.net/npm/@alphatype/alda-js/src/index.js"></script>

Quick Start

import Alda from '@alphatype/alda-js'

const font = Alda.load(aldaJsonString)  // → AldaFont

// Look up a glyph
const glyph = font.getGlyphByChar('가')
console.log(glyph.skeleton)  // stroke array

// Play animation
const anim = font.getAnimation('write')
console.log(anim.tracks)

// Active FX
console.log(font.getEnabledFx())

API

Alda.load(jsonStringOrObject) → AldaFont

Parse and validate an Alda document. Throws TypeError with a list of validation errors if the document is invalid.

Alda.isValid(data) → boolean

Returns true if data is a structurally valid Alda document.

AldaFont

| Method | Returns | Description | |---|---|---| | .getGlyph(unicode) | AldaGlyph \| null | Look up by hex codepoint e.g. 'AC00' | | .getGlyphByChar(char) | AldaGlyph \| null | Look up by character e.g. '가' | | .getAnimation(id) | AldaAnimation \| null | Look up animation by id | | .getEnabledFx() | AldaFx[] | All FX with enabled: true | | .toJSON() | string | Serialize back to .alda JSON | | .meta | AldaMeta | Font metadata | | .glyphs | AldaGlyph[] | All glyphs | | .animations | AldaAnimation[] | All animations | | .fx | AldaFx[] | All FX |

Alda.brush

Brush math utilities based on the elliptical brush model S = √(rx × ry).

| Method | Description | |---|---| | .computeS(rx, ry) | S = √(rx·ry) — geometric mean (size scalar) | | .computeRy(S, rx) | ry = S²/rx — recover ry when S is fixed | | .computeRoundness(rx, ry) | (ry/rx)×100 — roundness % | | .scale(brush, factor) | Scale brush preserving ratio and angle | | .normalize(brush?) | Fill missing fields with defaults |

Format

See spec/alda-spec-v0.1.md for the full format specification.

A minimal .alda file:

{
  "alda": "0.1",
  "meta": {
    "name": "My Font",
    "upm": 1000,
    "ascender": 800,
    "descender": -200
  },
  "glyphs": [
    {
      "unicode": "AC00",
      "name": "가",
      "advance": 550,
      "skeleton": [
        {
          "id": "stroke-0",
          "points": [
            { "x": 275, "y": 750, "type": "move" },
            { "x": 275, "y": 50,  "type": "line" }
          ],
          "width_profile": [30, 25]
        }
      ],
      "brush": { "rx": 14, "ry": 6, "angle": -0.3, "roundness": 43 }
    }
  ]
}

License

MIT © Alphatype