fontTools is a library for manipulating fonts, written in Python. The project includes the TTX tool, that can convert TrueType and OpenType fonts to and from an XML text format, which is also called TTX. It supports TrueType, OpenType, AFM and to an extent Type 1 and some Mac-specific formats. The project has an `MIT open-source license <https://github.com/fonttools/fonttools/blob/master/LICENSE>`_. Among other things this means you can use it free of charge.
If you would like to contribute to its development, you can clone the repository from GitHub, install the package in 'editable' mode and modify the source code in place. We recommend creating a virtual environment, using the Python 3 `venv <https://docs.python.org/3/library/venv.html>`_ module::
See the Optional Requirements section below for details about module-specific dependencies that must be installed in select cases.
TTX – From OpenType and TrueType to XML and Back
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Once installed you can use the ttx command to convert binary font files (.otf, .ttf, etc) to the TTX XML format, edit them, and convert them back to binary format. TTX files have a .ttx file extension::
ttx /path/to/font.otf
ttx /path/to/font.ttx
The TTX application can be used in two ways, depending on what platform you run it on:
* As a command line tool (Windows/DOS, Unix, macOS)
* By dropping files onto the application (Windows, macOS)
TTX detects what kind of files it is fed: it will output a ``.ttx`` file when it sees a ``.ttf`` or ``.otf``, and it will compile a ``.ttf`` or ``.otf`` when the input file is a ``.ttx`` file. By default, the output file is created in the same folder as the input file, and will have the same name as the input file but with a different extension. TTX will never overwrite existing files, but if necessary will append a unique number to the output filename (before the extension) such as ``Arial#1.ttf``.
When using TTX from the command line there are a bunch of extra options. These are explained in the help text, as displayed when typing ``ttx -h`` at the command prompt. These additional options include:
* specifying the folder where the output files are created
* specifying which tables to dump or which tables to exclude
* merging partial .ttx files with existing .ttf or .otf files
* listing brief table info instead of dumping to .ttx
TrueType fonts use glyph indices (GlyphIDs) to refer to glyphs in most places. While this is fine in binary form, it is really hard to work with for humans. Therefore we use names instead.
The glyph names are either extracted from the ``CFF`` table or the ``post`` table, or are derived from a Unicode ``cmap`` table. In the latter case the Adobe Glyph List is used to calculate names based on Unicode values. If all of these methods fail, names are invented based on GlyphID (eg ``glyph00142``)
It is possible that different glyphs use the same name. If this happens, we force the names to be unique by appending #n to the name (n being an integer number.) The original names are being kept, so this has no influence on a "round tripped" font.
Because the order in which glyphs are stored inside the binary font is important, we maintain an ordered list of glyph names in the font.
Please see the :py:mod:`fontTools.ttx` documentation for additional details.
The fontTools Python library provides a convenient way to programmatically edit font files::
>>> from fontTools.ttLib import TTFont
>>> font = TTFont('/path/to/font.ttf')
>>> font
<fontTools.ttLib.TTFont object at 0x10c34ed50>
>>>
A selection of sample Python programs is in the `Snippets directory <https://github.com/fonttools/fonttools/blob/master/Snippets/>`_ of the fontTools repository.
Please navigate to the respective area of the documentation to learn more about the available modules in the fontTools library.
Optional dependencies are detailed by module in the list below with the ``Extra`` setting that automates ``pip`` dependency installation when this is supported.
The module exports a ElementTree-like API for reading/writing XML files, and allows to use as the backend either the built-in ``xml.etree`` module or `lxml <https://lxml.de>`__. The latter is preferred whenever present, as it is generally faster and more secure.
When you run ``tox`` without arguments, the tests are executed for all the environments listed in the ``tox.ini````envlist``. The current Python interpreters defined for tox testing must be available on your system ``PATH``.
fontTools development is ongoing in an active community of developers that includes professional developers employed at major software corporations and type foundries as well as hobbyists.
Feature requests and bug reports are always welcome at https://github.com/fonttools/fonttools/issues/
The best place for end-user and developer discussion about the fontTools project is the `fontTools gitter channel <https://gitter.im/fonttools-dev/Lobby>`_. There is also a development https://groups.google.com/d/forum/fonttools-dev mailing list for continuous integration notifications.
