Class: Fontisan::Variation::VariationConverter

Inherits:
Object
  • Object
show all
Includes:
TableAccessor
Defined in:
lib/fontisan/variation/converter.rb

Overview

Converts variation data between TrueType (gvar) and CFF2 (blend) formats

This class enables format conversion while preserving variation data:

  • gvar tuples → CFF2 blend operators

  • CFF2 blend operators → gvar tuples

Process for gvar → blend:

  1. Extract tuple variations from gvar

  2. Map tuple regions to blend regions

  3. Embed blend operators in CharStrings at control points

  4. Encode delta values in blend format

Process for blend → gvar:

  1. Parse CharStrings with blend operators

  2. Extract blend deltas and regions

  3. Map to gvar tuple format

  4. Build gvar table structure

Examples:

Converting gvar to CFF2 blend

converter = VariationConverter.new(font, axes)
blend_data = converter.gvar_to_blend(glyph_id)

Converting CFF2 blend to gvar

converter = VariationConverter.new(font, axes)
tuple_data = converter.blend_to_gvar(glyph_id)

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from TableAccessor

#clear_variation_cache, #clear_variation_table, #has_variation_table?, #require_variation_table, #variation_table

Constructor Details

#initialize(font, axes) ⇒ VariationConverter

Initialize converter

Parameters:



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# File 'lib/fontisan/variation/converter.rb', line 46

def initialize(font, axes)
  @font = font
  @axes = axes || []
  @variation_tables = {}
end

Instance Attribute Details

#axes ⇒ Array<VariationAxisRecord> (readonly)

Returns Variation axes.

Returns:

  • (Array<VariationAxisRecord>) —

    Variation axes



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# File 'lib/fontisan/variation/converter.rb', line 40

def axes
  @axes
end

#font ⇒ TrueTypeFont, OpenTypeFont (readonly)

Returns Font instance.

Returns:



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# File 'lib/fontisan/variation/converter.rb', line 37

def font
  @font
end

Instance Method Details

#blend_to_gvar(_glyph_id) ⇒ Hash?

Convert CFF2 blend operators to gvar tuple format for a glyph

Parameters:

  • glyph_id (Integer) —

    Glyph ID

Returns:

  • (Hash, nil) —

    Tuple data or nil



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# File 'lib/fontisan/variation/converter.rb', line 75

def blend_to_gvar(_glyph_id)
  return nil unless has_variation_table?("CFF2")

  cff2 = variation_table("CFF2")
  return nil unless cff2

  # Get CharString with blend operators
  # This is a placeholder - full implementation would parse CharString
  # and extract blend operator data

  # Convert blend data to tuples
  # Placeholder for full implementation
  nil
end

#can_convert? ⇒ Boolean

Check if variation data can be converted

Returns:

  • (Boolean) —

    True if conversion possible



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# File 'lib/fontisan/variation/converter.rb', line 93

def can_convert?
  !@axes.empty? && (
    has_variation_table?("gvar") ||
    has_variation_table?("CFF2")
  )
end

#gvar_to_blend(glyph_id) ⇒ Hash?

Convert gvar tuples to CFF2 blend format for a glyph

Parameters:

  • glyph_id (Integer) —

    Glyph ID

Returns:

  • (Hash, nil) —

    Blend data or nil



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# File 'lib/fontisan/variation/converter.rb', line 56

def gvar_to_blend(glyph_id)
  return nil unless has_variation_table?("gvar")
  return nil unless has_variation_table?("glyf")

  gvar = variation_table("gvar")
  return nil unless gvar

  # Get tuple variations for this glyph
  tuple_data = gvar.glyph_tuple_variations(glyph_id)
  return nil unless tuple_data

  # Convert tuples to blend format
  convert_tuples_to_blend(tuple_data)
end