Class: EXIFR::TIFF::Field

Inherits:
Object
  • Object
show all
Defined in:
lib/tiff.rb

Overview

:nodoc:

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(data, pos) ⇒ Field

Returns a new instance of Field.



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# File 'lib/tiff.rb', line 459

def initialize(data, pos)
  @tag, count, @offset = data.readshort(pos), data.readlong(pos + 4), data.readlong(pos + 8)

  case data.readshort(pos + 2)
  when 1, 6 # byte, signed byte
    # TODO handle signed bytes
    len, pack = count, proc { |d| d }
  when 2 # ascii
    len, pack = count, proc { |d| d.strip }
  when 3, 8 # short, signed short
    # TODO handle signed
    len, pack = count * 2, proc { |d| d.unpack(data.short + '*') }
  when 4, 9 # long, signed long
    # TODO handle signed
    len, pack = count * 4, proc { |d| d.unpack(data.long + '*') }
  when 5, 10
    len, pack = count * 8, proc do |d|
      r = []
      d.unpack(data.long + '*').each_with_index do |v,i|
        i % 2 == 0 ? r << [v] : r.last << v
      end
      r.map do |f|
        if f[1] == 0 # allow NaN and Infinity
          f[0].to_f.quo(f[1])
        else
          Rational.respond_to?(:reduce) ? Rational.reduce(*f) : f[0].quo(f[1])
        end
      end
    end
  end

  if len && pack
    start = len > 4 ? @offset : (pos + 8)
    @value = [pack[data[start..(start + len - 1)]]].flatten
  end
end

Instance Attribute Details

#offset ⇒ Object (readonly)

Returns the value of attribute offset.



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# File 'lib/tiff.rb', line 457

def offset
  @offset
end

#tag ⇒ Object (readonly)

Returns the value of attribute tag.



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# File 'lib/tiff.rb', line 457

def tag
  @tag
end

#value ⇒ Object (readonly)

Returns the value of attribute value.



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# File 'lib/tiff.rb', line 457

def value
  @value
end