Module: Fontisan::TrueTypeFontExtensions

Included in:
TrueTypeFont
Defined in:
lib/fontisan/true_type_font_extensions.rb

Overview

Extension module for TrueTypeFont providing table-based construction.

Extended into TrueTypeFont from true_type_font.rb so that TrueTypeFont.from_tables(...) is available whenever the class itself is loaded.

Instance Method Summary collapse

Instance Method Details

#from_tables(tables) ⇒ TrueTypeFont

Create font from hash of tables

This is used during font conversion when we have tables but not a file.

Parameters:

  • tables (Hash<String, String>) —

    Map of table tag to binary data

Returns:



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# File 'lib/fontisan/true_type_font_extensions.rb', line 16

def from_tables(tables)
  font = new
  font.initialize_storage
  font.loading_mode = LoadingModes::FULL

  font.table_data = tables

  num_tables = tables.size
  max_power = 0
  n = num_tables
  while n > 1
    n >>= 1
    max_power += 1
  end

  search_range = (1 << max_power) * 16
  entry_selector = max_power
  range_shift = (num_tables * 16) - search_range

  font.header.sfnt_version = 0x00010000 # TrueType
  font.header.num_tables = num_tables
  font.header.search_range = search_range
  font.header.entry_selector = entry_selector
  font.header.range_shift = range_shift

  font.tables.clear
  tables.each_key do |tag|
    entry = TableDirectory.new
    entry.tag = tag
    entry.checksum = 0
    entry.offset = 0
    entry.table_length = tables[tag].bytesize
    font.tables << entry
  end

  font
end