Class: Fontisan::Converters::WoffWriter

Inherits:
Object
  • Object
show all
Includes:
ConversionStrategy
Defined in:
lib/fontisan/converters/woff_writer.rb

Overview

WOFF font writer for creating WOFF files from TTF/OTF fonts

[‘WoffWriter`](lib/fontisan/converters/woff_writer.rb) handles conversion from TrueType/OpenType fonts to WOFF format using zlib compression. This implements the WOFF 1.0 specification for web font optimization.

**WOFF Format Features:**

  • Individual table compression with zlib

  • Optional metadata block (compressed XML)

  • Optional private data block

  • Proper header and table directory structure

  • Cross-platform compatibility

**Compression Strategy:**

  • Each table is compressed individually for optimal ratios

  • Tables smaller than compression threshold remain uncompressed

  • Metadata and private data are compressed when present

  • All data is properly aligned and padded

Examples:

Converting TTF to WOFF

writer = Fontisan::Converters::WoffWriter.new
woff_data = writer.write_font(ttf_font, metadata: xml_metadata)
File.write("output.woff", woff_data)

With compression options

writer = Fontisan::Converters::WoffWriter.new(
  compression_level: 9,  # Maximum compression
  compression_threshold: 100  # Bytes - tables smaller than this stay uncompressed
)
woff_data = writer.write_font(ttf_font)

Constant Summary collapse

WOFF_SIGNATURE =

WOFF signature constant

0x774F4646
WOFF_VERSION_MAJOR =

WOFF version 1.0

1
WOFF_VERSION_MINOR = 
0
DEFAULT_COMPRESSION_LEVEL =

Default compression settings

6
DEFAULT_COMPRESSION_THRESHOLD =

bytes - don’t compress smaller tables

100

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from ConversionStrategy

#supports?, #validate

Constructor Details

#initialize(options = {}) ⇒ WoffWriter

Initialize writer with compression options

Parameters:

  • options (Hash) (defaults to: {}) —

    Writer options

Options Hash (options):

  • :compression_level (Integer) —

    zlib compression level (0-9)

  • :compression_threshold (Integer) —

    minimum table size to compress

  • :metadata_xml (String) —

    optional metadata XML

  • :private_data (String) —

    optional private data



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# File 'lib/fontisan/converters/woff_writer.rb', line 72

def initialize(options = {})
  @compression_level = options[:compression_level] || DEFAULT_COMPRESSION_LEVEL
  @compression_threshold = options[:compression_threshold] || DEFAULT_COMPRESSION_THRESHOLD
  @metadata_xml = options[:metadata_xml]
  @private_data = options[:private_data]

  validate_compression_level!
end

Instance Attribute Details

#compression_level ⇒ Object

Compression level (0-9, where 9 is maximum)



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# File 'lib/fontisan/converters/woff_writer.rb', line 54

def compression_level
  @compression_level
end

#compression_threshold ⇒ Object

Minimum table size to compress (bytes)



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# File 'lib/fontisan/converters/woff_writer.rb', line 57

def compression_threshold
  @compression_threshold
end

#metadata_xml ⇒ Object

Optional metadata XML



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# File 'lib/fontisan/converters/woff_writer.rb', line 60

def metadata_xml
  @metadata_xml
end

#private_data ⇒ Object

Optional private data



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# File 'lib/fontisan/converters/woff_writer.rb', line 63

def private_data
  @private_data
end

Instance Method Details

#convert(font, options = {}) ⇒ String

Convert font to WOFF format

Parameters:

  • font (TrueTypeFont, OpenTypeFont) —

    Source font

  • options (Hash) (defaults to: {}) —

    Additional options for this conversion

Returns:

  • (String) —

    WOFF file data as binary string

Raises:

  • (ArgumentError) —

    if font is invalid



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# File 'lib/fontisan/converters/woff_writer.rb', line 87

def convert(font, options = {})
  validate_font(font)

  # Override instance options with per-conversion options
  metadata = options[:metadata_xml] || @metadata_xml
  private_data = options[:private_data] || @private_data

  write_font(font, metadata: metadata, private_data: private_data)
end

#supported_conversions ⇒ Array<Array<Symbol>>

Get supported conversions

Returns:

  • (Array<Array<Symbol>>) —

    Supported conversion pairs



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# File 'lib/fontisan/converters/woff_writer.rb', line 100

def supported_conversions
  [
    %i[ttf woff],
    %i[otf woff],
  ]
end

#write_font(font, metadata: nil, private_data: nil) ⇒ String

Write font data to WOFF format

Parameters:

  • font (TrueTypeFont, OpenTypeFont) —

    Source font

  • metadata (String, nil) (defaults to: nil) —

    Optional metadata XML

  • private_data (String, nil) (defaults to: nil) —

    Optional private data

Returns:

  • (String) —

    WOFF file data



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# File 'lib/fontisan/converters/woff_writer.rb', line 113

def write_font(font, metadata: nil, private_data: nil)
  # Collect all table data from font
  tables_data = collect_tables_data(font)

  # Compress tables
  compressed_tables = compress_tables(tables_data)

  # Build WOFF file
  build_woff_file(compressed_tables, font, metadata, private_data)
end