Ttfautohint by Werner Lemberg is a free font utility, which goal is a 99% automated hinting process for web fonts, acting as a platform for finely hand-tuned hinting. Ttfautohint is a library written in C that takes a TrueType font as the input, removes its bytecode instructions (if any), and returns a new font where all glyphs are bytecode hinted using the information given by FreeType’s auto-hinting module. The idea is to provide the excellent quality of the auto-hinter on platforms that don’t use FreeType.
The library has a single API function, TTF_autohint, which is described here.
Bundled with the library there are two front-end programs, ttfautohint and ttfautohintGUI, being a command line program and an application with a Graphics User Interface (GUI), respectively.
The ttfautohint library brings the excellent quality of FreeType rendering to platforms that don’t use FreeType, yet require hinting for text to look good – like Microsoft Windows. Roughly speaking, it converts the glyph analysis done by FreeType’s auto-hinting module to TrueType bytecode. Internally, the auto-hinter’s algorithm resembles PostScript hinting methods; it thus combines all three hinting methods.
The simple interface of the front-ends (both on the command line and with the GUI) allows quick hinting of a whole font with a few mouse clicks or a single command on the prompt. As a result, you get better rendering results with web browsers, for example.
Across Windows rendering environments today, fonts processed with ttfautohint look best with ClearType enabled. This is the default for Windows 7. Good visual results are also seen in recent MacOS X versions and GNU/Linux systems (including Android, ChromeOS, and other mobile operating systems) that use FreeType for rendering glyphs.
The goal of the project is to generate a ‘first pass’ of hinting that font developers can refine further for ultimate quality.