FreeType Glyph Conventions

Version 2.1

Copyright 1998-2000 David Turner (
Copyright 2000 The FreeType Development Team (

This document presents the core conventions used within the FreeType library to manage font and glyph data. It is a must-read for all developers who need to understand digital typography, especially if you want to use the FreeType 2 library in your projects.

Table of Contents

I. Basic Typographic Concepts

1. Font files, format and information
2. Character images and mappings
3. Character and font metrics

II. Glyph outlines

1. Pixels, points and device resolutions
2. Vectorial representation
3. Hinting and bitmap rendering

III. Glyph metrics

1. Baseline, pens and layouts
2. Typographic metrics and bounding boxes
3. Bearings and advances
4. The effects of grid-fitting
5. Text widths and bounding box

IV. Kerning

1. Kerning pairs
2. Applying kerning

V. Text processing

1. Writing simple text strings
2. Sub-pixel positioning
3. Simple kerning
4. Right-to-left layouts
5. Vertical layouts
6. WYSIWYG text layouts

VI. FreeType Outlines

1. FreeType outline description and structure
2. Bounding and control box computations
3. Coordinates, scaling, and grid-fitting

VII. FreeType bitmaps

1. Vectorial versus pixel coordinates
2. FreeType bitmap and pixmap descriptor
3. Converting outlines into bitmaps and pixmaps