Class: PureJPEG::Huffman::FrequencyCounter

Inherits:
Object
  • Object
show all
Defined in:
lib/pure_jpeg/huffman/encoder.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ FrequencyCounter

Returns a new instance of FrequencyCounter.



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# File 'lib/pure_jpeg/huffman/encoder.rb', line 102

def initialize
  @dc_frequencies = Array.new(256, 0)
  @ac_frequencies = Array.new(256, 0)
  @prev_dc = Hash.new(0)
end

Instance Attribute Details

#ac_frequencies ⇒ Object (readonly)

Returns the value of attribute ac_frequencies.



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# File 'lib/pure_jpeg/huffman/encoder.rb', line 100

def ac_frequencies
  @ac_frequencies
end

#dc_frequencies ⇒ Object (readonly)

Returns the value of attribute dc_frequencies.



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# File 'lib/pure_jpeg/huffman/encoder.rb', line 100

def dc_frequencies
  @dc_frequencies
end

Instance Method Details

#observe_block(zigzag, state_key) ⇒ Object 



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# File 'lib/pure_jpeg/huffman/encoder.rb', line 108

def observe_block(zigzag, state_key)
  diff = zigzag[0] - @prev_dc[state_key]
  @prev_dc[state_key] = zigzag[0]

  cat = Encoder.category(diff)
  @dc_frequencies[cat] += 1

  Encoder.each_ac_symbol(zigzag) do |symbol|
    @ac_frequencies[symbol] += 1
  end
end