Codehead's Corner
Random ramblings on hacking, coding, fighting with infrastructure and general tech
Codehead’s Bitmap Font Generator
Posted: 17 Mar 2015 at 00:08 by Codehead

One of the big problems OpenGL runs into after you’ve got your first few polygons flying around the screen is the lack of a standard method for generating text within the API.

A few techniques have evolved to tackle the problem:

Pre-generated string textures

The simplest and fastest method, a texture is pre-built for each piece of text that needs to be displayed. This is quick to render at run time, but isn’t very flexible or efficient.

Polygon glyphs created from outline font definitions

This method produces high quality, scalable text, but this is also the slowest approach due to the overhead of generating and rendering the glyph polygons.

WGL and GLUT extensions

These extensions do a great job of text rendering. However, these libraries are not universally available on all systems and I have a bad habit of trying to be portable and platform independent.

Bitmapped fonts

Bitmap fonts are fast, flexible and platform independent. However, there are some limitations: Quality suffers when scaling up the texture and the number of possible characters in a font bitmap is limited. Extended or Unicode character sets with accents or non-latin symbols are not well supported.

A bitmapped font is simply an atlas texture containing a collection of glyphs and symbols. (Note: the purple lines are a visual aid, they do not appear on the actual texture.)

A simple font bitmap

The grid layout means that the calculation required to select any given character is quick and simple.

The area containing the selected characters can then be mapped onto a series of polygons to create dynamic strings of text.

A basic string composed of sub texture quads

Adding width information to the glyphs allows the textured quads to be overlapped to create better looking text with variable character widths.

The string with variable widths added

There are quite a few bitmap font generators around, but I couldn’t find one that provided all the features I wanted. So I wrote my own.

Codehead's Bitmap Font Generator

Codehead’s Bitmap Font Generator (CBFG) is now at version 1.45 and supports the following features:

  • DIB rendering of font gives best font output, regardless of users screen settings
  • Global or per character position and width adjustment
  • Texture Sizes from 16×16 up to 4096×4096
  • Zoom up to 400% for accurate tweaking of character positions
  • Anti-aliasing or ClearType (XP+) for smoother looking fonts
  • Control of font width
  • Font preview option
  • TGA export option
  • BMP output option
  • BFF output in 8, 24 and 32bit colour depths
  • C++ example source code for loading and rendering BFF files
  • Binary font data export
  • Font info dump option
  • User configurable colours and startup parameters

Many people have made useful suggestions that have been implemented in CBFG, and the tool has been used on the following projects:

Downloads

CBFG Packages

Windows Installer Package

Files only zip

Source Code

CBFG has been open sourced under the BSD licence. You can get v1.45 on GitHub

BFF Loading Code

C/C++ - included in zip/installer.

Android by Codehead

O’Caml by Einar (local mirror)

The Future

CBFG hasn’t been in active development for a few years now, but there are still a few features I always wanted to add:

ToDo List

  • State save option
  • Merge/Extract font image

Wish List

  • Export in other font generator formats
  • Edit font image
  • Unicode support

Known Issues

Cleartype system setting can override antialias settings in application.

Categories: Projects CBFG
Tags: #OpenGL #Font

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