Class: Fontisan::Tables::Cff2::VariationDataExtractor

Inherits:
Object
  • Object
show all
Defined in:
lib/fontisan/tables/cff2/variation_data_extractor.rb

Overview

Variation data extractor for CFF2 Variable Store

Extracts regions and deltas from the Variable Store and provides utilities for working with variation data.

Reference: OpenType spec - Item Variation Store Reference: Adobe Technical Note #5177 (CFF2)

Examples:

Extracting variation data

extractor = VariationDataExtractor.new(variable_store)
regions = extractor.regions
deltas = extractor.deltas_for_item(item_index)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(variable_store) ⇒ VariationDataExtractor

Initialize extractor with Variable Store data

Parameters:

  • variable_store (Hash) —

    Variable Store from CFF2TableReader



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 31

def initialize(variable_store)
  @variable_store = variable_store
  @regions = variable_store[:regions] || []
  @item_variation_data = variable_store[:item_variation_data] || []
end

Instance Attribute Details

#item_variation_data ⇒ Array<Hash> (readonly)

Returns Item variation data.

Returns:

  • (Array<Hash>) —

    Item variation data



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 26

def item_variation_data
  @item_variation_data
end

#regions ⇒ Array<Hash> (readonly)

Returns Extracted regions.

Returns:

  • (Array<Hash>) —

    Extracted regions



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 23

def regions
  @regions
end

#variable_store ⇒ Hash (readonly)

Returns Variable Store data.

Returns:

  • (Hash) —

    Variable Store data



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 20

def variable_store
  @variable_store
end

Instance Method Details

#all_deltas(data_index: 0) ⇒ Array<Array<Integer>>

Get all deltas for all items

Parameters:

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

    Item variation data index (default 0)

Returns:

  • (Array<Array<Integer>>) —

    Array of delta sets



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 75

def all_deltas(data_index: 0)
  return [] if data_index >= @item_variation_data.size

  @item_variation_data[data_index][:delta_sets] || []
end

#axis_count ⇒ Integer

Get number of axes from first region

Returns:

  • (Integer) —

    Number of axes



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 127

def axis_count
  return 0 if @regions.empty?

  @regions.first[:axis_count] || 0
end

#blend_value(item_index, base_value, scalars, data_index: 0) ⇒ Float

Calculate blended value for an item at specific coordinates

Parameters:

  • item_index (Integer) —

    Item index

  • base_value (Numeric) —

    Base value to blend

  • scalars (Array<Float>) —

    Region scalars for each region

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

    Item variation data index (default 0)

Returns:

  • (Float) —

    Blended value



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 88

def blend_value(item_index, base_value, scalars, data_index: 0)
  deltas = deltas_for_item(item_index, data_index: data_index)
  return base_value.to_f unless deltas

  indices = region_indices(data_index: data_index)

  # Apply blend: result = base + Σ(delta[i] * scalar[region_index[i]])
  result = base_value.to_f
  deltas.each_with_index do |delta, i|
    region_index = indices[i]
    next unless region_index

    scalar = scalars[region_index] || 0.0
    result += delta.to_f * scalar
  end

  result
end

#deltas_for_item(item_index, data_index: 0) ⇒ Array<Integer>?

Get deltas for a specific item

Parameters:

  • item_index (Integer) —

    Item index

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

    Item variation data index (default 0)

Returns:

  • (Array<Integer>, nil) —

    Deltas for the item, or nil if not found



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 42

def deltas_for_item(item_index, data_index: 0)
  return nil if data_index >= @item_variation_data.size

  item_data = @item_variation_data[data_index]
  return nil if item_index >= item_data[:delta_sets].size

  item_data[:delta_sets][item_index]
end

#has_data? ⇒ Boolean

Check if Variable Store has data

Returns:

  • (Boolean) —

    True if Variable Store contains data



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 136

def has_data?
  !@regions.empty? && !@item_variation_data.empty?
end

#item_count(data_index: 0) ⇒ Integer

Get number of items in item variation data

Parameters:

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

    Item variation data index (default 0)

Returns:

  • (Integer) —

    Number of items



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 65

def item_count(data_index: 0)
  return 0 if data_index >= @item_variation_data.size

  @item_variation_data[data_index][:item_count] || 0
end

#region(region_index) ⇒ Hash?

Get region by index

Parameters:

  • region_index (Integer) —

    Region index

Returns:

  • (Hash, nil) —

    Region data or nil if not found



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 111

def region(region_index)
  return nil if region_index >= @regions.size

  @regions[region_index]
end

#region_coordinates ⇒ Array<Array<Hash>>

Extract all region coordinates as arrays

Useful for debugging and validation

Returns:

  • (Array<Array<Hash>>) —

    Array of regions with axis coordinates



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 145

def region_coordinates
  @regions.map do |region|
    region[:axes].map do |axis|
      {
        start: axis[:start_coord],
        peak: axis[:peak_coord],
        end: axis[:end_coord],
      }
    end
  end
end

#region_count ⇒ Integer

Get number of regions

Returns:

  • (Integer) —

    Total number of regions



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 120

def region_count
  @regions.size
end

#region_indices(data_index: 0) ⇒ Array<Integer>

Get region indices for item variation data

Parameters:

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

    Item variation data index (default 0)

Returns:

  • (Array<Integer>) —

    Region indices



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 55

def region_indices(data_index: 0)
  return [] if data_index >= @item_variation_data.size

  @item_variation_data[data_index][:region_indices] || []
end

#validate ⇒ Array<String>

Validate Variable Store structure

Returns:

  • (Array<String>) —

    Array of validation errors (empty if valid)



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# File 'lib/fontisan/tables/cff2/variation_data_extractor.rb', line 160

def validate
  errors = []

  # Check regions consistency
  if @regions.any?
    expected_axes = @regions.first[:axis_count]
    @regions.each_with_index do |region, i|
      unless region[:axis_count] == expected_axes
        errors << "Region #{i} has inconsistent axis_count: " \
                  "#{region[:axis_count]} vs #{expected_axes}"
      end

      unless region[:axes].size == expected_axes
        errors << "Region #{i} has #{region[:axes].size} axes, " \
                  "expected #{expected_axes}"
      end
    end
  end

  # Check item variation data
  @item_variation_data.each_with_index do |item_data, i|
    item_count = item_data[:item_count]
    delta_sets = item_data[:delta_sets]
    region_indices = item_data[:region_indices]

    unless delta_sets.size == item_count
      errors << "Item variation data #{i} has #{delta_sets.size} " \
                "delta sets, expected #{item_count}"
    end

    # Check each delta set has correct number of deltas
    delta_sets.each_with_index do |deltas, j|
      unless deltas.size == region_indices.size
        errors << "Delta set #{j} in data #{i} has #{deltas.size} " \
                  "deltas, expected #{region_indices.size}"
      end
    end

    # Check region indices are valid
    region_indices.each_with_index do |idx, j|
      if idx >= @regions.size
        errors << "Region index #{idx} at position #{j} in data #{i} " \
                  "exceeds region count #{@regions.size}"
      end
    end
  end

  errors
end