arbez-dmtx

Read and write Data Matrix barcodes from Python — with the native libdmtx library bundled in the wheel on every platform. No brew install / apt-get install, no compiler. Pure ctypes, so one small wheel per platform works on all of Python 3.10–3.15, including free-threaded 3.13t / 3.14t / 3.15t.

from arbez_dmtx import decode, encode
from PIL import Image

decode(Image.open("code.png"))
# [Decoded(data=b'Stegosaurus', rect=Rect(left=5, top=6, width=96, height=95))]

enc = encode(b"hello")
Image.frombytes("RGB", (enc.width, enc.height), enc.pixels).save("dmtx.png")

Install

pip install arbez-dmtx

That's it — the libdmtx shared library is inside the wheel. No system packages.

Supported platforms (wheels are published for these; there is no sdist, so pip install requires a matching wheel):

Not yet built: macOS x86_64 (Intel), Windows arm64. If you need one, open an issue.

Relationship to pylibdmtx

arbez-dmtx is a friendly, modernised continuation of pylibdmtx by Lawrence Hudson / the Natural History Museum (MIT). It vendors pylibdmtx's excellent ctypes wrapper and keeps the same public API, but closes the gaps that made pylibdmtx awkward to depend on in 2026:

Migrating is a one-line import swap — the function/return signatures match:

# before
from pylibdmtx.pylibdmtx import decode, encode
# after
from arbez_dmtx import decode, encode

If you only need this library on Windows, pylibdmtx already works great; the value here is everywhere else (and on the new free-threaded interpreters).

API

The full pylibdmtx surface is re-exported at the top level:

from arbez_dmtx import (
    decode, encode,                       # the two operations
    Decoded, Rect, Encoded,               # result types
    ENCODING_SCHEME_NAMES, ENCODING_SIZE_NAMES,  # encode() vocabularies
    PyLibDMTXError,                       # error type
    libdmtx_version,                      # bundled libdmtx version string
)

• decode(image, ...) accepts a PIL.Image, a numpy.ndarray (e.g. from OpenCV), or a (pixels, width, height) tuple, and the full libdmtx tuning surface: timeout, gap_size, shrink, shape, deviation, threshold, min_edge, max_edge, corrections, max_count. Returns a list of Decoded(data: bytes, rect: Rect).
• encode(data, scheme=None, size=None) → Encoded(width, height, bpp, pixels); scheme/size come from ENCODING_SCHEME_NAMES / ENCODING_SIZE_NAMES.

Why pure ctypes?

No compiled extension means (a) one py3-none-<platform> wheel covers every Python version — including the free-threaded builds, with no per-ABI matrix — and (b) importing it never re-enables the GIL; ctypes releases the GIL around each native call, so concurrent decode is safe on 3.13t/3.14t/3.15t.

License & attribution

Apache-2.0 (this wrapper). Bundles libdmtx (BSD-2-Clause, © Mike Laughton, Vadim A. Misbakh-Soloviov and others) and vendors the pylibdmtx ctypes wrapper (MIT, © Lawrence Hudson). Full notices in NOTICE; the libdmtx license also ships inside each wheel as THIRD_PARTY_LICENSES_libdmtx.txt.

Not affiliated with or endorsed by the pylibdmtx authors — just standing on their shoulders, gratefully.