FreeType Font Engine

FreeType is a freely available software library to render fonts.

FreeType is a freely available software library to render fonts.

The LVGL FreeType extension is an interface to the FreeType library, enabling you to generate font bitmaps at run time from most vector- and bitmap-font file formats.

For a detailed introduction, see: https://freetype.org/ .

Adding FreeType to Your Project

First, Download FreeType from the freetype2folder (and optionallyfreetype-docsandfreetype-demos) from its official repository. (The latest version is recommended.)

If you haven't already done so, now is a good time to get familiar with setting up and configuring this library. The above website is a good place to start, as is the README file in the top directory of the version you downloaded.

There are two ways to use FreeType:

For UNIX

For UNIX-like systems, the following is recommended to compile and install FreeType libraries.

• Enter the FreeType source code directory
• make
• sudo make install
• Add include path: /usr/include/freetype2 (for GCC: -I/usr/include/freetype2 -L/usr/local/lib)
• Link against library: freetype (for GCC: -L/usr/local/lib -lfreetype)

For Embedded Devices

For embedded devices, it is recommended to use the FreeType configuration files provided by LVGL:

• lvgl/src/libs/freetype/ftmodule.h
• lvgl/src/libs/freetype/ftoption.h

which only include the most commonly used modules and options, which is important to save limited FLASH space.

• Copy the FreeType source code to your project directory.
• Refer to the following Makefile for configuration:

# FreeType custom configuration header file
CFLAGS += -DFT2_BUILD_LIBRARY
CFLAGS += -DFT_CONFIG_MODULES_H=<lvgl/src/libs/freetype/ftmodule.h>
CFLAGS += -DFT_CONFIG_OPTIONS_H=<lvgl/src/libs/freetype/ftoption.h>

# FreeType include path
CFLAGS += -Ifreetype/include

# FreeType C source file
FT_CSRCS += freetype/src/base/ftbase.c
FT_CSRCS += freetype/src/base/ftbitmap.c
FT_CSRCS += freetype/src/base/ftdebug.c
FT_CSRCS += freetype/src/base/ftglyph.c
FT_CSRCS += freetype/src/base/ftinit.c
FT_CSRCS += freetype/src/base/ftstroke.c
FT_CSRCS += freetype/src/cache/ftcache.c
FT_CSRCS += freetype/src/gzip/ftgzip.c
FT_CSRCS += freetype/src/sfnt/sfnt.c
FT_CSRCS += freetype/src/smooth/smooth.c
FT_CSRCS += freetype/src/truetype/truetype.c
CSRCS += $(FT_CSRCS)

Usage

Set LV_USE_FREETYPE in lv_conf.h to 1.

Cache configuration:

• LV_FREETYPE_CACHE_FT_GLYPH_CNT Maximum number of cached glyphs., etc.

By default, the FreeType extension doesn't use LVGL's file system. You can simply pass the path to the font as usual on your operating system or platform.

If you want FreeType to use LVGL's memory allocation and file system interface, you can enable LV_FREETYPE_USE_LVGL_PORT in lv_conf.h, convenient for unified management. If you do this, you will need to exclude the configured FreeType library's ftsystem.c file from being compiled, since LVGL's lv_ftsystem.c has custom versions of the functions defined therein.

The font style supports Italic and Bold fonts processed by software, and can be set by using following values where style values are required:

• LV_FREETYPE_FONT_STYLE_NORMAL: Default style.
• LV_FREETYPE_FONT_STYLE_ITALIC: Italic style.
• LV_FREETYPE_FONT_STYLE_BOLD: Bold style.

These values can be combined, e.g. LV_FREETYPE_FONT_STYLE_BOLD | LV_FREETYPE_FONT_STYLE_ITALIC.

The FreeType extension also supports colored bitmap glyphs such as emojis. Note that only bitmaps are supported at this time. Colored vector graphics cannot be rendered. An example on how to draw a colored bitmap glyph is shown below.

Use the lv_freetype_font_create function to create a font. To delete a font, use lv_freetype_font_delete. For more detailed usage, please refer to the example code below.

Rendering vector fonts is supported with VGLite or ThorVG, when using vector fonts with ThorVG, it is possible to set a letter outline of a different color.

This is achieved by setting the style attributes with the lv_style_set_text_outline_width and lv_style_set_text_outline_color functions

You will have to account for the increased width and height of letter due to the added letter outline, to avoid letters overlapping space them out using lv_style_set_text_letter_space

To use vector fonts with ThorVG, you will have to enable LV_USE_VECTOR_GRAPHICS in lv_conf.h

See the lv_example_freetype_2_vector_font function for a usage example

Examples

Create a font with FreeType

Use a bitmap font to draw Emojis using FreeType

Freetype font kerning

API