Font Hinting Overview

Fontisan provides comprehensive support for font hints, including extraction, conversion, validation, and preservation. Hints are rendering instructions embedded in fonts that improve appearance at small sizes and low resolutions.

Hinting Systems

Fontisan supports two hinting systems:

System	Format	Storage	Type
TrueType	TTF	prep, fpgm, cvt tables	Bytecode instructions
PostScript	OTF	CFF Private DICT	Declarative hints

TrueType Instructions

Bytecode-based hints using instruction opcodes:

• SSW — Set Single Width
• SCVTCI — Set CVT Cut-In
• WCVTP — Write CVT in Pixels
• And many more...

Stored in:

• prep — Control Value Program
• fpgm — Font Program
• cvt — Control Value Table

PostScript Hints

Declarative hints using operators:

• hstem — Horizontal stem hints
• vstem — Vertical stem hints
• hintmask — Hint activation mask

Stored in CFF Private dictionaries.

Features

• Bidirectional Conversion — Convert hints between TrueType and PostScript
• Hint Extraction — Extract existing hints from TTF and OTF fonts
• Hint Application — Apply hints during format conversion
• Validation — Comprehensive validation of hint data
• Round-Trip Preservation — Maintain hint integrity during conversion cycles

Guides

• TrueType Hinting — TrueType instruction details
• PostScript Hinting — CFF hint parameters
• Hint Conversion — Bidirectional conversion
• Autohint — Automatic hinting

Quick Start

Check for Hints

font = Fontisan::FontLoader.load('font.ttf')

# Check TrueType hints
if font.tables['prep'] || font.tables['fpgm']
  puts "TrueType hints present"
end

# Check PostScript hints
if cff = font.tables['CFF']
  private_dict = cff.top_dicts.first[:private]
  if private_dict[:blue_values]
    puts "PostScript hints present"
  end
end

Convert with Hints

# Preserve hints during conversion
fontisan convert font.ttf --to otf --hinting-mode preserve

# Apply autohinting
fontisan convert font.ttf --to otf --autohint --hinting-mode auto