.. _lang-packs:

====================================
Installing additional language packs
====================================

OCRmyPDF uses Tesseract for OCR, and relies on its language packs for all languages.
On most platforms, English is installed with Tesseract by default, but not always.

Tesseract supports `most
languages <https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#languages>`__.
Languages are identified by standardized three-letter codes (called ISO 639-2 Alpha-3).
Tesseract's documentation also lists the three-letter code for your language.
Some are anglicized, e.g. Spanish is ``spa`` rather than ``esp``, while others
are not, e.g. German is ``deu``.

After you have installed a language pack, you can use it ``ocrmypdf -l <language>``,
for example ``ocrmypdf -l spa``. For multilingual documents, you can specify
all languages to be expected, e.g. ``ocrmypdf -l eng+fra`` for English and French.
English is assumed by default unless other language(s) are specified.

For Linux users, you can often find packages that provide language
packs:

.. code-block:: bash

   # Display a list of all Tesseract language packs
   apt-cache search tesseract-ocr

   # Install Chinese Simplified language pack
   apt-get install tesseract-ocr-chi-sim

You can then pass the ``-l LANG`` argument to OCRmyPDF to give a hint as
to what languages it should search for. Multiple languages can be
requested using either ``-l eng+fre`` (English and French) or
``-l eng -l fre``.
