Class: Fontisan::Woff2::TableTransformer

Inherits:
Object
  • Object
show all
Defined in:
lib/fontisan/woff2/table_transformer.rb

Overview

Table transformer for WOFF2 encoding

Woff2::TableTransformer handles table transformations that improve compression in WOFF2. The WOFF2 spec defines transformations for glyf/loca and hmtx tables.

Transformations implemented:

  • glyf/loca: Combined stream format with specialized encoding
  • hmtx: Delta encoding with 255UInt16 compression

Reference: https://www.w3.org/TR/WOFF2/#table_tranforms

Examples:

Transform tables for WOFF2

transformer = TableTransformer.new(font)
glyf_data = transformer.transform_table("glyf")

Constant Summary collapse

TRANSFORM_DISPATCH =

Transform a table for WOFF2 encoding

Per-tag transform method dispatch.

Returns:

  • (String, nil) —

    Transformed table data

{
  "glyf" => :transform_glyf,
  "loca" => :transform_loca,
  "hmtx" => :transform_hmtx,
}.freeze
TRANSFORM_VERSIONS =

Per-tag transform version constant.

{
  "glyf" => Directory::TRANSFORM_GLYF_LOCA,
  "loca" => Directory::TRANSFORM_GLYF_LOCA,
  "hmtx" => Directory::TRANSFORM_HMTX,
}.freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(font) ⇒ TableTransformer

Initialize transformer with font

Parameters:



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# File 'lib/fontisan/woff2/table_transformer.rb', line 27

def initialize(font)
  @font = font
end

Instance Attribute Details

#font ⇒ Object (readonly)

Returns Font object with table access.

Returns:

  • (Object) —

    Font object with table access



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# File 'lib/fontisan/woff2/table_transformer.rb', line 22

def font
  @font
end

Instance Method Details

#transform_table(tag) ⇒ Object 



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# File 'lib/fontisan/woff2/table_transformer.rb', line 49

def transform_table(tag)
  transform_method = TRANSFORM_DISPATCH[tag]
  return method(transform_method).call if transform_method

  # No transformation, return original data
  get_table_data(tag)
end

#transformable?(tag) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/fontisan/woff2/table_transformer.rb', line 57

def transformable?(tag)
  TRANSFORM_DISPATCH.key?(tag)
end

#transformation_version(tag) ⇒ Object 



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# File 'lib/fontisan/woff2/table_transformer.rb', line 61

def transformation_version(tag)
  TRANSFORM_VERSIONS.fetch(tag, Directory::TRANSFORM_NONE)
end