FreeType

Language: C

Graphics / Font Rendering

FreeType was developed to provide a high-quality, portable, and efficient library for font rendering. It is widely used in operating systems, GUI toolkits, games, and embedded systems where precise control over font rendering is needed.

FreeType is a C library for rendering fonts, supporting various font formats such as TrueType, OpenType, Type1, and CFF. It provides functionality to load, rasterize, and render glyphs for text display in applications.

Installation

linux: sudo apt install libfreetype6-dev
mac: brew install freetype
windows: Download binaries from https://www.freetype.org/download.html or build from source

Usage

FreeType allows developers to load font files, access glyph metrics, render glyphs into bitmaps or vector paths, and integrate with graphics libraries like Cairo or OpenGL for text rendering.

Initializing FreeType and loading a font

#include <ft2build.h>
#include FT_FREETYPE_H
#include <stdio.h>

int main() {
    FT_Library library;
    FT_Face face;

    if (FT_Init_FreeType(&library)) {
        printf("Could not initialize FreeType library\n");
        return 1;
    }

    if (FT_New_Face(library, "arial.ttf", 0, &face)) {
        printf("Could not load font\n");
        return 1;
    }

    printf("Font loaded: %s\n", face->family_name);

    FT_Done_Face(face);
    FT_Done_FreeType(library);
    return 0;
}

Initializes the FreeType library, loads a font file (`arial.ttf`), prints its family name, and cleans up resources.

Loading and rendering a glyph

#include <ft2build.h>
#include FT_FREETYPE_H
#include <stdio.h>

int main() {
    FT_Library library;
    FT_Face face;
    FT_Init_FreeType(&library);
    FT_New_Face(library, "arial.ttf", 0, &face);

    FT_Set_Pixel_Sizes(face, 0, 48);
    if (FT_Load_Char(face, 'A', FT_LOAD_RENDER)) {
        printf("Could not load glyph\n");
        return 1;
    }

    printf("Glyph bitmap width: %d, rows: %d\n", face->glyph->bitmap.width, face->glyph->bitmap.rows);

    FT_Done_Face(face);
    FT_Done_FreeType(library);
    return 0;
}

Loads a single character glyph ('A'), renders it to a bitmap, and prints its dimensions.

Rendering text to an image buffer

// Typically involves iterating through each character,
// loading glyphs, copying bitmap to a pixel buffer, and
// using a graphics library (e.g., SDL, Cairo) to display.

Accessing glyph metrics

// Use face->glyph->advance, face->glyph->bitmap_left, face->glyph->bitmap_top
// to compute positioning when drawing text manually.

Error Handling

FT_Err_Unknown_File_Format: Occurs when the font format is not recognized. Ensure the font file is valid and supported.
FT_Err_Cannot_Open_Resource: The font file could not be opened. Verify the path and file permissions.
FT_Err_Invalid_Argument: An invalid argument was passed to a FreeType function. Check parameters carefully.

Best Practices

Always initialize and clean up the FreeType library and faces.

Use appropriate pixel sizes and transformations for high-quality text.

Cache loaded glyphs to improve rendering performance.

Combine FreeType with a graphics library for display purposes.

Handle errors when loading fonts or glyphs to prevent crashes.

Official DocsGithub