Class: Fontisan::Tables::Maxp

Inherits:
Binary::BaseRecord show all
Defined in:
lib/fontisan/tables/maxp.rb

Overview

BinData structure for the ‘maxp’ (Maximum Profile) table

The maxp table contains memory and complexity limits for the font. It provides the number of glyphs and various maximum values needed for font rendering and processing.

The table has two versions:

  • Version 0.5 (0x00005000): CFF fonts - only version and numGlyphs

  • Version 1.0 (0x00010000): TrueType fonts - includes additional fields

Version 1.0 fields provide information about:

  • Glyph outline complexity (points, contours)

  • Composite glyph structure

  • TrueType instruction limitations

Reference: OpenType specification, maxp table docs.microsoft.com/en-us/typography/opentype/spec/maxp

Examples:

Reading a maxp table

data = File.binread("font.ttf", size, maxp_offset)
maxp = Fontisan::Tables::Maxp.read(data)
puts maxp.num_glyphs       # => 512
puts maxp.version          # => 1.0 or 0.5
puts maxp.truetype?        # => true or false

Constant Summary collapse

VERSION_0_5 =

Version 0.5 constant (CFF fonts)

0x00005000
VERSION_1_0 =

Version 1.0 constant (TrueType fonts)

0x00010000
TABLE_SIZE_V0_5 =

Minimum table size for version 0.5 (4 + 2 = 6 bytes)

6
TABLE_SIZE_V1_0 =

Full table size for version 1.0 (4 + 2 + 13×2 = 32 bytes)

32

Instance Method Summary collapse

Methods inherited from Binary::BaseRecord

#raw_data, read

Instance Method Details

#cff? ⇒ Boolean

Check if this is a CFF font (alias for version_0_5?)

Returns:

  • (Boolean) —

    True if CFF font, false otherwise



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# File 'lib/fontisan/tables/maxp.rb', line 138

def cff?
  version_0_5?
end

#expected_size ⇒ Integer

Get the expected table size based on version

Returns:

  • (Integer) —

    Expected size in bytes



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# File 'lib/fontisan/tables/maxp.rb', line 187

def expected_size
  version_1_0? ? TABLE_SIZE_V1_0 : TABLE_SIZE_V0_5
end

#truetype? ⇒ Boolean

Check if this is a TrueType font (alias for version_1_0?)

Returns:

  • (Boolean) —

    True if TrueType font, false otherwise



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# File 'lib/fontisan/tables/maxp.rb', line 131

def truetype?
  version_1_0?
end

#valid? ⇒ Boolean

Check if the table is valid

Returns:

  • (Boolean) —

    True if valid, false otherwise



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

def valid?
  # Version must be either 0.5 or 1.0
  return false unless version_0_5? || version_1_0?

  # Number of glyphs must be at least 1
  return false unless num_glyphs >= 1

  # For version 1.0, maxZones must be 1 or 2
  if version_1_0? && max_zones && !(max_zones >= 1 && max_zones <= 2)
    return false
  end

  true
end

#validate_structure! ⇒ Object Also known as: validate!

Validate the table and raise error if invalid

Raises:



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# File 'lib/fontisan/tables/maxp.rb', line 163

def validate_structure!
  unless version_0_5? || version_1_0?
    raise Fontisan::CorruptedTableError,
          "Invalid maxp version: expected 0x00005000 (0.5) or " \
          "0x00010000 (1.0), got 0x#{version_raw.to_s(16).upcase}"
  end

  unless num_glyphs >= 1
    raise Fontisan::CorruptedTableError,
          "Invalid number of glyphs: must be >= 1, got #{num_glyphs}"
  end

  if version_1_0? && max_zones && (max_zones < 1 || max_zones > 2)
    raise Fontisan::CorruptedTableError,
          "Invalid maxZones: must be 1 or 2, got #{max_zones}"
  end
end

#version ⇒ Float

Convert version from fixed-point to float

Version 0.5 (0x00005000) is a special case, not standard 16.16 fixed-point

Returns:

  • (Float) —

    Version number (1.0 or 0.5)



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# File 'lib/fontisan/tables/maxp.rb', line 103

def version
  case version_raw
  when VERSION_0_5
    0.5
  when VERSION_1_0
    1.0
  else
    fixed_to_float(version_raw)
  end
end

#version_0_5? ⇒ Boolean

Check if this is version 0.5 (CFF)

Returns:

  • (Boolean) —

    True if version 0.5, false otherwise



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# File 'lib/fontisan/tables/maxp.rb', line 124

def version_0_5?
  version_raw == VERSION_0_5
end

#version_1_0? ⇒ Boolean

Check if this is version 1.0 (TrueType)

Returns:

  • (Boolean) —

    True if version 1.0, false otherwise



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# File 'lib/fontisan/tables/maxp.rb', line 117

def version_1_0?
  version_raw == VERSION_1_0
end