dwg2png

dwg2png

dwg2png is a pure-Rust CLI that turns an opaque binary DWG (R13–R2018) into retrievable artifacts: one PNG per layout (Model space + paper sheets, with viewport projection), optional readable tiles, a position-referenced text layer (every label as exact text + pixel box — no OCR), and a JSON metadata index. It runs offline with no GPU, no C libraries, and no external CAD engine.

Use this skill to render DWGs, extract their text/metadata, or feed CAD drawings into a RAG/VLM pipeline.

Get the tool

Prefer the Docker image (self-contained, includes a font with broad script coverage); fall back to a release binary or building from source. Source repo: diskd-ai/dwg2png.

# A) Docker (build once from the repo)
git clone https://github.com/diskd-ai/dwg2png && cd dwg2png
docker build -t dwg2png:latest .

# B) Prebuilt binary (macOS arm64/x64, Linux x64, Windows x64)
gh release download --repo diskd-ai/dwg2png --pattern '*linux*'
tar -xzf dwg2png-*-linux-gnu.tar.gz   # -> ./dwg2png

# C) From source
cargo build --release --bin dwg2png   # -> target/release/dwg2png

Native runs need a TrueType font; default is macOS Arial. On Linux/Docker set DWG2PNG_FONT (the image sets it to DejaVu Sans) or pass --font /path.ttf. Use a font whose glyph coverage matches the drawings' labels.

Run it

# whole folder -> high-res pages + tiles + text layer + index
dwg2png input/ --out out --size 6000 --tiles --no-compare

# Docker equivalent
docker run --rm -v "$PWD/input:/work/input:ro" -v "$PWD/out:/work/out" \
  dwg2png:latest /work/input --out /work/out --size 6000 --tiles --no-compare

Inputs may be files or directories (recursed for *.dwg). Key flags:

• --out DIR — output root (default out)
• --size PX — long-edge pixels (default 3000, up to 12000)
• --tiles — also emit ~1500 px readable crops (--tile-size N to change)
• --font TTF — typeface (or DWG2PNG_FONT env)
• --no-compare — skip the ground-truth PDF comparison (no pdftoppm needed)

Full flag reference: see references/cli.md.

What it produces (under --out)

out/
  img/fNN-pMM.png        page previews (p00 = Model space, then paper sheets)
  tiles/fNN-pMM/rRcC.png readable crops + tiles.json (per-tile labels)
  labels/fNN-pMM.json    text layer: exact strings + pixel x,y,w,h + layer + color
  json/fNN.json          per-file index: layers, blocks, attributes, histogram
  report.html            self-contained report (toggleable SVG text overlay)

fNN = file index, pMM = page index. Output schemas: references/outputs.md.

Reading every label (the key idea)

CAD labels are sub-pixel against a large drawing extent, and VLMs downscale images on input — so a single raster never makes every label legible. Two channels solve this; use both:

1. Text layer (labels/*.json) — strings come straight from the DWG, so they are 100% accurate (no OCR), each anchored to a pixel box. This is the reliable channel for "read every label" and for grounded citations.
2. Tiles (--tiles) — ~1500 px crops where text is large enough to read visually; each tile's tiles.json carries the labels inside it.

Using it in a RAG / VLM pipeline

The text layer + index give OCR-free, positionally-grounded text; the tiles give readable image context. Build chunks from the labels and attach geometry as metadata for citations. A ready-made helper:

# cluster labels into embed-ready chunks (JSONL) with {file,page,layer,bbox}
python3 scripts/labels_to_chunks.py out/labels --out chunks.jsonl

Patterns (chunking, embedding, citation, multimodal): see references/rag.md.

Requirements & sizing

• Image ~81 MB; binary ~2.3 MB. No GPU/C deps.
• Typical file (≤1 MB): ~1–2 s, 200–450 MB RAM. Large 40–50 MB drawings: ~25–30 s, ~2.8 GB RAM (parse-bound) — give those a high-memory queue.
• Memory tracks DWG file size, not render resolution. Process one DWG per invocation; scale out with parallel workers/replicas.

Notes

• Not rendered (but counted/indexed): hatch fills, dimension geometry (its text is captured), leaders, lineweights. Drawings stay recognizable.
• A corrupt/unreadable DWG degrades to a placeholder via failsafe parsing instead of crashing — safe for batch ingestion.