engine-js

@pdf2md/engine — portable TypeScript + ONNX engine

Pure-JS PDF → Markdown. No Python, no sidecar binary. The same core runs under a Node CLI (here), an Obsidian desktop plugin, a browser extension, and eventually mobile — only device/dtype change.

Pipeline: pdf.js rasterizes each page → granite-docling-258M ONNX runs under transformers.js and emits DocTags → a JS DocTags→Markdown parser → MathJax repairs → the frozen vault package (<pdf-stem>/<pdf-stem>.md + images/ + meta.json, engine: "onnx-portable"). Anything that may have damaged the text is surfaced in the note — a warning banner, an inline marker at each affected page, and a conversion_warnings property — not only in meta.json.

Layout

File	Role	Needs the model?
src/doctags.ts	DocTags → Markdown (OTSL tables, <loc_*> bboxes, <formula> LaTeX)	no
src/mathjax.ts	Brace balancing / \tag / aligned repairs (ported from the Python bootstrap)	no
src/frontmatter.ts	Obsidian YAML frontmatter	no
src/pdf.ts	pdf.js raster + text layer + figure crops (@napi-rs/canvas)	no
src/vlm.ts	transformers.js load + page → DocTags	yes
src/meta.ts	meta.json shape (engine, model, timings, execution providers)	no
src/index.ts	Orchestrator convertPdf()	yes
src/cli.ts	pdf2md-js CLI	yes

Run

npm install
npm run typecheck        # tsc --noEmit over the whole package
npm run test:offline     # DocTags parser + MathJax repairs — no download

# First real convert downloads ~190 MB (q4f16) to the transformers.js cache:
npm run cli -- convert ../fixtures/attention.pdf --out out/
#   flags: --no-formulas  --ocr  --device cpu|webgpu|auto

# Cross-engine parity against the shared ground truth (downloads the model):
PDF2MD_RUN_MODEL=1 npm test

Status

Scaffold (M2 in progress). The no-model modules are real and unit-tested; the VLM path is fully wired but its first end-to-end run + fixture parity is the M2/M3 gate. See ../PLAN.md.

Model & licensing

onnx-community/granite-docling-258M-ONNX (Apache-2.0). Variants: fp32 ≈1.03 GB / fp16 ≈515 MB / int8 ≈260 MB / q4f16 ≈190 MB (default decoder). Downloaded on first convert; see ../docs/models.md. pdf.js (Apache-2.0), @napi-rs/canvas (MIT). MuPDF-WASM deliberately avoided (AGPL).