bakefont3

bakefont3 is a python3 module for rasterising font glyphs into a RGBA texture atlas and exporting metrics and kerning information, and a C library for loading that information.

An included example program shows how Bakefont3 can be used for fast & high-quality OpenGL text rendering.

Pack glyphs efficiently into a texture atlas
(using example-generate.py)

Make use of kerning information
(based on example-gl.c)

Use any beautiful truetype font you want
(realtime rendering using example-gl.c)

Support any language and locale with full unicode support
(realtime rendering using example-gl.c; depends on font support)
(only partial support for vertical writing - see limitations if you can help)

Features

• Unicode support
• customisable character ranges
• exports font metrics and kerning data as binary optimised for quick lookup
• efficient packing to reduce physical texture size
• can use all four colour channels to share space with other textures (can export RGBA, RGB, greyscale)
• suitable for efficient real-time rendering using OpenGL shaders
• supports square and rectangle texture atlases of any size
• metrics accurate up to 1/64th of a pixel (e.g. for supersampling)
• small .c loader - no heavy dependencies in client software
• pixel-perfect results for even the smallest text

Limitations

• fonts, sizes and styles must be known and generated in advance (slow!)
• for large text, vector graphics are better
• not ideal for rotated text (decent results with supersampling?)
• does not include a layout engine - just exports the metrics that one would use (but see example simple layout in example-gl.c)
• does not support RGBA glyphs - e.g. full colour emojis (yet)

Bakefont3 does not export vertical kerning information for vertical fonts. This can easily be fixed - please get in touch if you can help. This isn't a technical barrier: I just don't know what the correct result looks like and I don't have any fonts to test with.

Example Usage

Generate a font atlas / metrics / kerning pairs using bakefont3

A sample script, example-generate.py, is provided. You may like to edit it to select the fonts, sizes and characters to generate.

$ python3 example-generate.py

This file generates the following files:

test.bf3
test-rgba.png
test-r.png
test-g.png
test-b.png
test-a.png

test-rgba.png is a texture atlas containing rasterised glyphs in each colour channel. The other images show the individual channels, but you don't need them.

test.bf3 contains information about the fonts used, how to find characters in the texture atlas, metrics and kerning information for laying out text on a screen.

Load files generated by bakefont3

A sample program, example.c is provided. You may like to edit it to change the font data it tries to load.

bakefont3.h and bakefont3.c are an example interface for loading and querying bakefont3 data.

$ # Compile
$ gcc -std=c99 example.c bakefont3.h bakefont3.c -lm -o example.bin
# # Run
$ ./example.bin example/test.bf3 example/test-rgba.png

Render text with bakefont3

A sample program, example-gl.c is provided. You may like to edit it to change the font data it tries to load.

bakefont3.h and bakefont3.c are an example interface for loading and querying bakefont3 data.

$ # Compile
$ gcc -std=c99 example-gl.c bakefont3.c lib/png.c lib/gl3w.c lib/utf8.c -lm -lglfw -lGL -lpng -ldl  -Wall -Wextra -o example-gl.bin
# # Run
$ ./example-gl.bin example/test.bf3 example/test-rgba.png

Dependencies

For generating fonts using bakefont3:

• Python3 and modules Pillow, numpy, freetype-py

Example:

$ sudo apt-get install libfreetype6
$ sudo pip3 install Pillow numpy freetype-py

For the Python example program:

• Roboto and Roboto Mono fonts (from fonts.google.com)
• Arial font from Microsoft (search msttcorefonts)

For the C example program:

• Maths: link with -lm
• a C compiler (e.g. gcc, clang)

For the C/OpenGL example program:

• You will also need libpng and libglfw

Example:

$ sudo apt-get install libglfw3 libglfw3-dev libpng12-0 libpng12-dev

Useful notes

When talking about font faces and glyphs, what do terms like ascent, descent, kerning, etc. mean?

See 1, 2, 3, 4

Font sizes are given in pixels.

Typographic dpi is always 72. At 72ppi, 1pt == 1px. Convert as necessary for different devices.

What is the "26.6 fixed float" format?

This encodes a Real number as a signed 32 bit integer. Divide by 64.0 to get the Real value. Or, multiply a Real value by 64.0 and cast to a signed 32 bit integer to encode it.

One of the reasons these are used is because unlike floats, they compare precisely - e.g. a font size of 13.5pt can be identified exactly.

(Freetype also has a "2.14 fixed float" format but you don't need to know anything about this).

Why use all four colour channels to bake the texture atlas?

If you are using the texture atlas on its own, you gain nothing by doing this and may as well just generate the greyscale version (bakefont3 can do that, too).

However, you sometimes want to combine several textures - like the glyphs, GUI images, game graphics, etc. into one big RGBA texture as an optimisation to avoid texture switching on the GPU.

For example, you might extend your text rendering code to draw full-colour icons and emojis aligned with your text in the same batch.

Copyright Status of Rasterised Glyphs

This does depend: copyright law in the U.S protects the font, but not the typeface. In Europe, the typeface is usually protected.

The safest and most ethical way to handle this is to think of Bakefont3 as something that creates a derived work. Copyrighted data goes in, copyrighted data comes out.

That means that the output of a Bakefont3 program should inherit the same copyright and license as the input. In the case of multiple inputs by different authors, the output shares all these copyrights and licenses. The licenses must not conflict.

Most open source fonts share the same one or two permissive licenses (fonts.google.com is a great place for this), so this is usually quite simple in practice.

It's also worth knowing that many open source font licenses say that you can't use the same name for a derived work. Bakefont3 by design makes it easy to use your own generic names for fonts (it's also fine to say something like "My Font based on Original Font").

COPYING

Bakefont3 is free and open source software.

Did you publish software that uses Bakefont3? Did it save you time? Did it add value to your software? If so, please consider supporting the author.

bakefont3

Copyright © 2015 - 2017 Ben Golightly <golightly.ben@googlemail.com>

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