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Treepoem pre-commit

A cleverly named, but very simple python barcode renderer wrapping the BWIPP library and ghostscript command line tool.


Install from pip:

python -m pip install treepoem

Python 3.6 to 3.10 supported.

You'll also need Ghostscript installed. On Ubuntu/Debian this can be installed with:

apt-get install ghostscript

On Mac OS X use:

brew install ghostscript

Otherwise refer to your distribution's package manager, though it's likely to be called ghostscript too.

There's a known issue with rendering on Ghostscript 9.22+ where images are smeared. See GitHub Issue #124 and its associated links for more details. Ghostscript merged a fix in version 9.26 and common barcodes seem to work from then on, though still with some smearing.

You can check your Ghostscript version with:

gs --version

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generate_barcode(barcode_type: str, data: str | bytes, options: dict[str, str | bool] | None=None) -> EpsImageFile

Generates a barcode and returns it as a PIL image file object (specifically, a PIL.EpsImagePlugin.EpsImageFile).

barcode_type is the name of the barcode type to generate (see below).

data is a str or bytes of data to embed in the barcode - the amount that can be embedded varies by type.

options is a dictionary of strings-to-strings of extra options to be passed to BWIPP, as per its docs.

For example, this generates a QR code image, and saves it to a file using standard PIL

>>> import treepoem
>>> image = treepoem.generate_barcode(
...     barcode_type="qrcode",  # One of the BWIPP supported codes.
...     data="barcode payload",
... )
>>> image.convert("1").save("barcode.png")

If your barcode image is monochrome, with no additional text or coloring, converting the Image object to monochrome as shown above (image.convert('1')) will likely reduce its file size.

barcode_types: dict[str, BarcodeType]

This is a dict of the ~100 names of the barcode types that the vendored version of BWIPP supports: its keys are strs of the barcode type encoder names, and the values are instances of BarcodeType.


A class representing meta information on the types. It has two attributes:

  • type_code - the value needed for the barcode_type argument of generate_barcode() to use this type.
  • description - the human level description of the type which has two str.

Only these common types are used in the test suite:

Command-line interface

Treepoem also includes a simple command-line interface to the functionality of generate_barcode. For example, these commands will generate two QR codes with identical contents, but different levels of error correction (see QR Code Options):

$ treepoem -o barcode1.png -t qrcode "This is a test" eclevel=H
$ treepoem -o barcode2.png -t qrcode "^084his is a test" eclevel=L parse

Complete usage instructions are shown with treepoem --help.

What's so clever about the name?


Bark ode.

Tree poem.

Updating BWIPP

For development of treepoem, when there's a new BWIPP release:

  1. Download the latest monolithic zip file from
  2. Unzip the files into src/treepoem/postscriptbarcode
  3. Remove the unneded docs subdirectory.
  4. Run from the root of the repo to update the barcode types that treepoem knows about.
  5. Add a CHANGELOG note about the upgrade.
  6. Commit and make a pull request, for examples see


Barcode rendering for Python supporting QRcode, Aztec, PDF417, I25, Code128, Code39 and many more types.





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