---
title: secondmouseau/swiftdxf
framework: Swift Package Catalog
role: article
path: packages/secondmouseau/swiftdxf
---

# secondmouseau/swiftdxf

A small, dependency-free **Swift reader for ASCII DXF** — AutoCAD's *Drawing Interchange Format* —

## What it reads

The 2D entity set that dominates real-world drawings, from the `ENTITIES` (model-space) section:

| DXF entity | `DXF.Entity` case | |---|---| | `LINE` | `.line(a, b, layer, color)` | | `CIRCLE` | `.circle(center, radius, …)` | | `ARC` | `.arc(center, radius, startDeg, endDeg, …)` | | `ELLIPSE` | `.ellipse(center, majorAxis, ratio, startParam, endParam, …)` | | `POINT` | `.point(at, …)` | | `TEXT`, `MTEXT` | `.text(at, height, rotationDeg, string, …)` | | `LWPOLYLINE`, `POLYLINE`/`VERTEX` | `.polyline(vertices, closed, …)` — each vertex carries its **bulge** | | `DIMENSION` | `.dimension(Dimension)` — semantic measurement only, not the rendered arrow/text glyphs |

Entities it does not model (e.g. `INSERT`, `SPLINE`, `HATCH`) are **skipped, not fatal**.

`Drawing` also exposes header essentials: `version` (`$ACADVER`), `insUnits` (`$INSUNITS`), and the declared `extMin` / `extMax` extents (`$EXTMIN` / `$EXTMAX`), plus a computed `bounds` over the entities actually read.

### Behaviours worth knowing

- **Encoding.** Files are decoded as UTF-8 when valid, otherwise **CP932 / Shift-JIS** — the common   code page for DXF exported by Japanese CAD tools (e.g. Jw_cad). Because CP932 is an ASCII superset,   the group-code structure is unaffected either way. AutoCAD `\U+XXXX` text escapes are decoded. - **Line endings & padding.** Handles LF / CRLF / CR and R12-style space-padded group codes (`  0`). - **Ellipse normalisation.** DXF requires `ratio = minor/major ≤ 1`. Files that emit `ratio > 1`   (a swapped major axis) are normalised to the canonical form — same curve, valid axis — so consumers   like OCCT's `Geom_Ellipse` (which demands `majorRadius ≥ minorRadius`) get correct geometry. This   matches `ezdxf`'s normalisation exactly. - **Binary DXF** is detected and rejected (`Error.binaryUnsupported`) — convert to ASCII DXF first. - **Model space only.** Mirrors what `ezdxf`'s `modelspace()` iterates; `BLOCKS` definitions are not   expanded.

## Correctness: tested against an oracle

`tools/oracle.py` runs `ezdxf` over the same files and emits per-file entity counts **and** a geometry digest (the sum of every defining coordinate scalar, in document order). The `dxfdump` executable emits the identical shape from SwiftDXF:

```bash swift run dxfdump drawing.dxf | python3 -m json.tool ```

Across an 11-file corpus (~62,000 entities, mixed R12 drawings incl. Jw_cad exports), SwiftDXF matches `ezdxf` **exactly** — every entity count and every coordinate scalar, to the bit. The `Tests/SwiftDXFTests/CorpusOracleTests.swift` suite pins those ezdxf-derived counts as a regression gate (skipped when the corpus is absent; point `DXF_CORPUS` at a folder of `.dxf` files to run).

## Install

```swift .package(url: "https://github.com/SecondMouseAU/SwiftDXF.git", from: "0.1.0"), // target dependency: .product(name: "SwiftDXF", package: "SwiftDXF") ```

## Scope

A focused 2D reader, not a full DXF/DWG toolkit. Out of scope for now: DWG, binary DXF, block/insert expansion, splines, hatches, dimensions, and writing. (DXF *writing* for the JWW format lives in [SwiftJWW](https://github.com/SecondMouseAU/SwiftJWW).)

## License

MIT — see [LICENSE](LICENSE).

## Package Metadata

Repository: secondmouseau/swiftdxf

Default branch: main

README: README.md