Class: Fontisan::Tables::Cff::CharStringRebuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/fontisan/tables/cff/charstring_rebuilder.rb

Overview

Rebuilds CharStrings INDEX with modified CharStrings

CharStringRebuilder provides high-level interface for modifying CharStrings in a CFF font. It extracts all CharStrings from the source INDEX, allows modifications through a callback, and rebuilds the INDEX with updated CharString data.

Use Cases:

  • Per-glyph hint injection

  • CharString optimization

  • Subroutine insertion

  • Any operation requiring CharString modification

Examples:

Inject hints into specific glyphs

rebuilder = CharStringRebuilder.new(charstrings_index)
rebuilder.modify_charstring(42) do |operations|
  # Insert hint operations at beginning
  hint_ops = [
    { type: :operator, name: :hstem, operands: [10, 20] }
  ]
  hint_ops + operations
end
new_index_data = rebuilder.rebuild

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(source_index, stem_count: 0) ⇒ CharStringRebuilder

Initialize rebuilder with source CharStrings INDEX

Parameters:

  • source_index (CharstringsIndex) —

    Source CharStrings INDEX

  • stem_count (Integer) (defaults to: 0) —

    Number of stem hints (for parsing hintmask)



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 44

def initialize(source_index, stem_count: 0)
  @source_index = source_index
  @stem_count = stem_count
  @modifications = {}
end

Instance Attribute Details

#modifications ⇒ Hash (readonly)

Returns Modified CharString data by glyph index.

Returns:

  • (Hash) —

    Modified CharString data by glyph index



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 38

def modifications
  @modifications
end

#source_index ⇒ CharstringsIndex (readonly)

Returns Source CharStrings INDEX.

Returns:



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 35

def source_index
  @source_index
end

Instance Method Details

#batch_modify(glyph_indices) {|glyph_index, operations| ... } ⇒ Object

Batch modify multiple CharStrings

More efficient than calling modify_charstring multiple times.

Parameters:

  • glyph_indices (Array<Integer>) —

    Glyph indices to modify

Yields:

  • (glyph_index, operations) —

    Block to modify each glyph

Yield Parameters:

  • glyph_index (Integer) —

    Current glyph index

  • operations (Array<Hash>) —

    Parsed operations

Yield Returns:

  • (Array<Hash>) —

    Modified operations



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 111

def batch_modify(glyph_indices)
  glyph_indices.each do |glyph_index|
    modify_charstring(glyph_index) do |operations|
      yield(glyph_index, operations)
    end
  end
end

#charstring_data(glyph_index) ⇒ String

Get CharString data (modified or original)

Parameters:

  • glyph_index (Integer) —

    Glyph index

Returns:

  • (String) —

    CharString binary data



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 139

def charstring_data(glyph_index)
  @modifications[glyph_index] || @source_index[glyph_index]
end

#clear_modifications ⇒ Object

Clear all modifications



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 159

def clear_modifications
  @modifications.clear
end

#modification_count ⇒ Integer

Get count of modified glyphs

Returns:

  • (Integer) —

    Number of modified glyphs



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 154

def modification_count
  @modifications.size
end

#modified?(glyph_index) ⇒ Boolean

Check if glyph has been modified

Parameters:

  • glyph_index (Integer) —

    Glyph index

Returns:

  • (Boolean) —

    True if modified



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 147

def modified?(glyph_index)
  @modifications.key?(glyph_index)
end

#modify_all {|glyph_index, operations| ... } ⇒ Object

Modify all CharStrings

Applies the same modification to every glyph.

Yields:

  • (glyph_index, operations) —

    Block to modify each glyph

Yield Parameters:

  • glyph_index (Integer) —

    Current glyph index

  • operations (Array<Hash>) —

    Parsed operations

Yield Returns:

  • (Array<Hash>) —

    Modified operations



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 127

def modify_all
  (0...@source_index.count).each do |i|
    modify_charstring(i) do |operations|
      yield(i, operations)
    end
  end
end

#modify_charstring(glyph_index) {|operations| ... } ⇒ Object

Modify a CharString by glyph index

The block receives the parsed operations for the glyph and should return modified operations.

Parameters:

  • glyph_index (Integer) —

    Glyph index (0 = .notdef)

Yields:

  • (operations) —

    Block to modify operations

Yield Parameters:

  • operations (Array<Hash>) —

    Parsed operations

Yield Returns:

  • (Array<Hash>) —

    Modified operations



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 59

def modify_charstring(glyph_index)
  # Get original CharString data
  original_data = @source_index[glyph_index]
  return unless original_data

  # Parse to operations
  parser = CharStringParser.new(original_data, stem_count: @stem_count)
  operations = parser.parse

  # Apply modification
  modified_operations = yield(operations)

  # Build new CharString
  new_data = CharStringBuilder.build_from_operations(modified_operations)

  # Store modification
  @modifications[glyph_index] = new_data
end

#rebuild ⇒ String

Rebuild CharStrings INDEX with modifications

Creates new INDEX with modified CharStrings, keeping unmodified CharStrings unchanged.

Returns:

  • (String) —

    Binary CharStrings INDEX data



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 84

def rebuild
  # Collect all CharString data (modified and unmodified)
  charstrings = []

  (0...@source_index.count).each do |i|
    charstrings << if @modifications.key?(i)
                     # Use modified CharString
                     @modifications[i]
                   else
                     # Use original CharString
                     @source_index[i]
                   end
  end

  # Build INDEX
  IndexBuilder.build(charstrings)
end

#stem_count=(count) ⇒ Object

Update stem count (needed for hintmask parsing)

Parameters:

  • count (Integer) —

    Number of stem hints



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# File 'lib/fontisan/tables/cff/charstring_rebuilder.rb', line 166

def stem_count=(count)
  @stem_count = count
end