Class: Fontisan::Hints::TrueTypeHintExtractor

Inherits:
Object
  • Object
show all
Defined in:
lib/fontisan/hints/truetype_hint_extractor.rb

Overview

Extracts rendering hints from TrueType glyph data

TrueType uses bytecode instructions for hinting. This extractor analyzes glyph instruction sequences and converts them into universal Hint objects for format-agnostic representation.

Supported TrueType Instructions:

  • MDAP - Move Direct Absolute Point (stem positioning)
  • MDRP - Move Direct Relative Point (stem width)
  • IUP - Interpolate Untouched Points (smooth interpolation)
  • SHP - Shift Point (point adjustments)
  • ALIGNRP - Align to Reference Point (alignment)
  • DELTA - Delta instructions (pixel-level adjustments)

Examples:

Extract hints from a glyph

extractor = TrueTypeHintExtractor.new
hints = extractor.extract(glyph)

Constant Summary collapse

MDAP_RND =

TrueType instruction opcodes

0x2E
MDAP_NORND = 
0x2F
MDRP_MIN_RND_BLACK = 
0xC0
IUP_Y = 
0x30
IUP_X = 
0x31
SHP = 
[0x32, 0x33].freeze
ALIGNRP = 
0x3C
DELTAP1 = 
0x5D
DELTAP2 = 
0x71
DELTAP3 = 
0x72

Instance Method Summary collapse

Instance Method Details

#extract(glyph) ⇒ Array<Hint>

Extract hints from TrueType glyph

Parameters:

  • glyph (Glyph) —

    TrueType glyph with instructions

Returns:

  • (Array<Hint>) —

    Extracted hints



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# File 'lib/fontisan/hints/truetype_hint_extractor.rb', line 64

def extract(glyph)
  return [] if glyph.nil? || glyph.empty?
  return [] unless glyph.respond_to?(:instructions)

  instructions = glyph.instructions || []
  return [] if instructions.empty?

  parse_instructions(instructions)
end

#extract_from_font(font) ⇒ Models::HintSet

Extract complete hint data from TrueType font

This extracts both font-level hints (fpgm, prep, cvt tables) and per-glyph hints from glyph instructions.

Parameters:

Returns:



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# File 'lib/fontisan/hints/truetype_hint_extractor.rb', line 43

def extract_from_font(font)
  hint_set = Models::HintSet.new(format: "truetype")

  # Extract font-level programs
  hint_set.font_program = extract_font_program(font)
  hint_set.control_value_program = extract_control_value_program(font)
  hint_set.control_values = extract_control_values(font)

  # Extract per-glyph hints
  extract_glyph_hints(font, hint_set)

  # Update metadata
  hint_set.has_hints = !hint_set.empty?

  hint_set
end