Font Triangulation Tool

A Python library that converts TrueType/OpenType font glyph outlines into triangular meshes.

Features

• ✅ Full Sample Point Triangulation: All line points and quadratic/cubic curve sample points are added to the vertex set
• ✅ No Additional Vertices: Triangulation only uses contour sample points without adding any new vertices
• ✅ Inner/Outer Contour Differentiation: Outer contours displayed in red, inner contours (holes) in blue
• ✅ Complete Vertex Display: All sample points visualized

Technical Principles

Core Workflow

1. Font Parsing: Use fontTools to read font files and extract glyph outlines
2. Contour Sampling: Discretize Bezier curves into sample points
3. Direction Detection: Distinguish outer contours (counter-clockwise) from inner contours (clockwise) based on area sign
4. Hierarchy Construction: Establish parent-child relationships between outer and inner contours
5. Triangulation: Use shapely for polygon triangulation, ensuring triangles are within valid regions

Contour Direction Convention

Contour Type	Direction	Area Sign
Outer Contour	Counter-clockwise	Negative
Inner Contour (Hole)	Clockwise	Positive

Installation

pip install numpy matplotlib fonttools shapely

Usage

Method 1: Interactive Mode

python font2tri_lib.py

The program will automatically search for system fonts (KaiTi, Microsoft YaHei, SimSun), then you can input characters for triangulation.

Method 2: Programmatic Call

from font2tri_lib import FontTriangulator

# Initialize triangulator
ft = FontTriangulator(r"C:\Windows\Fonts\simkai.ttf")

# Process single character
ft.run('中')

# Batch process characters
for char in ['中', '国', '字', 'A', 'O']:
    ft.run(char)

Method 3: Test Script

python test_all_chars.py

Core Class Documentation

FontTriangulator

The core class for font triangulation, providing glyph contour extraction and triangulation functionality.

Methods

Method	Description	Parameters
__init__(font_path)	Initialize triangulator	font_path: Path to font file
extract_sampled_contours(char, curve_steps=20)	Extract character contour sample points	char: Single character; curve_steps: Curve sampling steps
triangulate_from_contour_points(contours)	Triangulate contours	contours: List of contour point arrays
show(char, contours, vs, fs)	Visualize results	character, contours, vertices, faces
run(char, curve_steps=20)	Complete execution flow	character and curve sampling steps

Output Example

The program displays three plots:

1. Left: Original contours (outer contours red, inner contours blue)
2. Middle: Triangulation result (light blue fill, blue edges)
3. Right: Vertex set (red dots showing all sample points)

Console output example:

【中】Done
  Contours: 1
  Vertices: 168 (lines + curve samples)
  Triangles: 324

Supported Font Formats

• TrueType (.ttf)
• TrueType Collection (.ttc)
• OpenType (.otf)

System Requirements

• Python 3.6+
• Windows (system font search path is Windows-specific)

Project Structure

font2tri_outline/
├── font2tri_lib.py      # Core library file
├── test_all_chars.py    # Test script
├── README.md            # Documentation (Chinese)
└── readme_en.md         # Documentation (English)

License

MIT License