@catlabtech/webcvt-font

Self-written, dependency-free font-container converter for webcvt: convert between sfnt (TTF/OTF) and WOFF 1.0 entirely client-side.

This is pure container repackaging — it rewraps the same font tables, it does not render glyphs or convert outlines.

What it does

• sfnt → WOFF: read the sfnt tables, zlib-deflate each (kept stored when compression doesn't help), and wrap them in a WOFF header + directory.
• WOFF → sfnt: inflate each table, rebuild the sfnt offset table + directory, and recompute table checksums + head.checkSumAdjustment.
• The output extension follows the font's flavor: an OTTO (CFF) font becomes .otf, otherwise .ttf.
• readFontMeta exposes basics from the name/head/maxp tables (family/subfamily/full name, unitsPerEm, numGlyphs).

Install

npm install @catlabtech/webcvt-core @catlabtech/webcvt-font

Usage

import { parseSfnt, serializeWoff, parseWoff, serializeSfnt } from '@catlabtech/webcvt-font';

const woff = await serializeWoff(parseSfnt(ttfBytes));   // TTF/OTF → WOFF
const ttf = serializeSfnt(await parseWoff(woffBytes));    // WOFF → TTF/OTF

Via the backend (opt-in registration — never auto-registers):

import { convert, defaultRegistry } from '@catlabtech/webcvt-core';
import { FontBackend } from '@catlabtech/webcvt-font';

defaultRegistry.register(new FontBackend());
const woff = await convert(ttfBlob, { format: 'woff' });
const ttf = await convert(woffBlob, { format: 'ttf' });

Not supported

• WOFF 2.0 (wOF2) — rejected with a typed error. It needs Brotli (unavailable in DecompressionStream) plus glyf-table transform reconstruction.
• ttf ↔ otf outline/CFF conversion — only sfnt↔WOFF repackaging is performed (a TrueType font stays TrueType; a CFF font stays CFF).
• TrueType/OpenType Collections (ttcf).

Security

64 MiB input cap, ≤4096 tables, a per-table size cap, and a cumulative decompression-bomb cap enforced while inflating; every table offset/length is bounds-checked against the input.

License

MIT