Universal Outline Model

The Fontisan Universal Outline Model (UOM) provides a format-agnostic representation of glyph contours that enables seamless conversion between different font formats.

Overview

The UOM is based on a self-stable algorithm for converting soft glyph contours to outline format. This architecture allows:

• Importing glyphs from any font format (TrueType, OpenType, CFF)
• Converting glyph elements between formats
• Operating on outlines with transformations
• Serialization and storage

Core Components

Locker

The Locker is an object-oriented model for storing imported outlines and glyphs. Storage is based on monotonic spirals computed from 2D points and curves.

Features:

• Invisible conversion from TrueType, CFF OpenType, and ColorGlyph formats
• Preserves original glyph geometry
• Supports compound glyph decomposition

Translator

The Translator is an object-oriented model for converting between PostScript CFF charsets.

Features:

• PostScript Type 2/3/composite encoding and decoding
• CFF INDEX structure building
• CFF DICT structure building
• Charset conversion

ColorGlyph

ColorGlyph provides support for layered CFF color glyphs with on-demand rasterization.

Features:

• Composite font support
• Multi-layer color font representation
• CFF fonts stacked on top of each other
• Advanced color glyphs
• Raster image support (PNG/JPG) combined with TrueType outlines

Universal Fonts

Fontisan provides universal font capabilities:

Capability	Description
Import	Import TrueType contours into UOM
Operate	Transform, clean, improve, and render outlines
Convert	Convert UOM contours to TTF/OTF
Serialize	Save and share font structures
Color Support	Work with advanced color fonts

Universal Glyphs

The universal glyph model enables:

• Universal Outline Model (UOM) for TrueType contours and CFF color glyphs
• Repository for custom fonts
• Custom Unicode assignments and configuration
• Outline import/export (TrueType and OTF/CFF)
• Rendering for advanced font types
• Universal layer stacking for color glyph combinations

Universal Color Layers

Universal color layers support advanced color font operations:

Feature	Description
Import	Import embedded TTF/OTF color layers
Assemble	Assemble from individual TTF/OTF slices
Manage	Advanced layer map management in TTF color fonts
Blend	Advanced color layer blending style management
Convert	Gray/Overprint/Color-Full image comps and layer conversion
Raster	Smart vector combos from raster images
PNG	Import and generate PNG block ruler layers

Curve Conversion

The UOM handles bidirectional curve conversion:

• TrueType → CFF: Quadratic to cubic curve conversion
• CFF → TrueType: Cubic to quadratic curve conversion
• CFF2 Support: Variable font CFF2 outlines

Ruby API

Loading Outlines

require 'fontisan'

# Load font and access universal outlines
font = Fontisan::FontLoader.load('font.ttf')

# Access glyphs through universal model
glyphs = font.glyphs

glyphs.each do |glyph|
  # Access universal outline representation
  outline = glyph.universal_outline

  # Get contour count
  puts "Glyph #{glyph.name}: #{outline.contour_count} contours"

  # Access points and curves
  outline.contours.each do |contour|
    contour.commands.each do |cmd|
      case cmd.type
      when :move_to
        puts "  Move to #{cmd.x}, #{cmd.y}"
      when :line_to
        puts "  Line to #{cmd.x}, #{cmd.y}"
      when :quad_to
        puts "  Quadratic curve to #{cmd.x}, #{cmd.y}"
      when :curve_to
        puts "  Cubic curve to #{cmd.x}, #{cmd.y}"
      end
    end
  end
end

Converting Outlines

# Convert between curve types
converter = Fontisan::Converters::CurveConverter.new

# TrueType (quadratic) to CFF (cubic)
cff_outlines = converter.quad_to_cubic(truetype_outlines)

# CFF (cubic) to TrueType (quadratic)
ttf_outlines = converter.cubic_to_quad(cff_outlines)

Related Documentation

• Curve Converter API — Curve conversion details
• Outline Converter API — Full outline conversion
• Font Conversion Guide — Conversion workflows
• Color Fonts Guide — Color font support