Class: Origami::Filter::CCITTFax

Inherits:
Object
  • Object
show all
Includes:
Origami::Filter
Defined in:
lib/origami/filters/ccitt.rb

Overview

Class representing a Filter used to encode and decode data with CCITT-facsimile compression algorithm.

Defined Under Namespace

Classes: DecodeParms

Constant Summary collapse

EOL = 
codeword('000000000001')
RTC = 
codeword('000000000001' * 6)
WHITE_TERMINAL_ENCODE_TABLE = 
{
  0   => codeword('00110101'), 
  1   => codeword('000111'),
  2   => codeword('0111'),
  3   => codeword('1000'),
  4   => codeword('1011'),
  5   => codeword('1100'),
  6   => codeword('1110'),
  7   => codeword('1111'),
  8   => codeword('10011'),
  9   => codeword('10100'),
  10  => codeword('00111'),
  11  => codeword('01000'),
  12  => codeword('001000'),
  13  => codeword('000011'),
  14  => codeword('110100'),
  15  => codeword('110101'),
  16  => codeword('101010'),
  17  => codeword('101011'),
  18  => codeword('0100111'),
  19  => codeword('0001100'),
  20  => codeword('0001000'),
  21  => codeword('0010111'),
  22  => codeword('0000011'),
  23  => codeword('0000100'),
  24  => codeword('0101000'),
  25  => codeword('0101011'),
  26  => codeword('0010011'),
  27  => codeword('0100100'),
  28  => codeword('0011000'),
  29  => codeword('00000010'),
  30  => codeword('00000011'),
  31  => codeword('00011010'),
  32  => codeword('00011011'),
  33  => codeword('00010010'),
  34  => codeword('00010011'),
  35  => codeword('00010100'),
  36  => codeword('00010101'),
  37  => codeword('00010110'),
  38  => codeword('00010111'),
  39  => codeword('00101000'),
  40  => codeword('00101001'),
  41  => codeword('00101010'),
  42  => codeword('00101011'),
  43  => codeword('00101100'),
  44  => codeword('00101101'),
  45  => codeword('00000100'),
  46  => codeword('00000101'),
  47  => codeword('00001010'),
  48  => codeword('00001011'),
  49  => codeword('01010010'),
  50  => codeword('01010011'),
  51  => codeword('01010100'),
  52  => codeword('01010101'),
  53  => codeword('00100100'),
  54  => codeword('00100101'),
  55  => codeword('01011000'),
  56  => codeword('01011001'),
  57  => codeword('01011010'),
  58  => codeword('01011011'),
  59  => codeword('01001010'),
  60  => codeword('01001011'),
  61  => codeword('00110010'),
  62  => codeword('00110011'),
  63  => codeword('00110100')
}
WHITE_TERMINAL_DECODE_TABLE = 
WHITE_TERMINAL_ENCODE_TABLE.invert
BLACK_TERMINAL_ENCODE_TABLE = 
{
  0   => codeword('0000110111'), 
  1   => codeword('010'),
  2   => codeword('11'),
  3   => codeword('10'),
  4   => codeword('011'),
  5   => codeword('0011'),
  6   => codeword('0010'),
  7   => codeword('00011'),
  8   => codeword('000101'),
  9   => codeword('000100'),
  10  => codeword('0000100'),
  11  => codeword('0000101'),
  12  => codeword('0000111'),
  13  => codeword('00000100'),
  14  => codeword('00000111'),
  15  => codeword('000011000'),
  16  => codeword('0000010111'),
  17  => codeword('0000011000'),
  18  => codeword('0000001000'),
  19  => codeword('00001100111'),
  20  => codeword('00001101000'),
  21  => codeword('00001101100'),
  22  => codeword('00000110111'),
  23  => codeword('00000101000'),
  24  => codeword('00000010111'),
  25  => codeword('00000011000'),
  26  => codeword('000011001010'),
  27  => codeword('000011001011'),
  28  => codeword('000011001100'),
  29  => codeword('000011001101'),
  30  => codeword('000001101000'),
  31  => codeword('000001101001'),
  32  => codeword('000001101010'),
  33  => codeword('000001101011'),
  34  => codeword('000011010010'),
  35  => codeword('000011010011'),
  36  => codeword('000011010100'),
  37  => codeword('000011010101'),
  38  => codeword('000011010110'),
  39  => codeword('000011010111'),
  40  => codeword('000001101100'),
  41  => codeword('000001101101'),
  42  => codeword('000011011010'),
  43  => codeword('000011011011'),
  44  => codeword('000001010100'),
  45  => codeword('000001010101'),
  46  => codeword('000001010110'),
  47  => codeword('000001010111'),
  48  => codeword('000001100100'),
  49  => codeword('000001100101'),
  50  => codeword('000001010010'),
  51  => codeword('000001010011'),
  52  => codeword('000000100100'),
  53  => codeword('000000110111'),
  54  => codeword('000000111000'),
  55  => codeword('000000100111'),
  56  => codeword('000000101000'),
  57  => codeword('000001011000'),
  58  => codeword('000001011001'),
  59  => codeword('000000101011'),
  60  => codeword('000000101100'),
  61  => codeword('000001011010'),
  62  => codeword('000001100110'),
  63  => codeword('000001100111')
}
BLACK_TERMINAL_DECODE_TABLE = 
BLACK_TERMINAL_ENCODE_TABLE.invert
WHITE_CONFIGURATION_ENCODE_TABLE = 
{
  64    => codeword('11011'),
  128   => codeword('10010'),
  192   => codeword('010111'),
  256   => codeword('0110111'),
  320   => codeword('00110110'),
  384   => codeword('00110111'),
  448   => codeword('01100100'),
  512   => codeword('01100101'),
  576   => codeword('01101000'),
  640   => codeword('01100111'),
  704   => codeword('011001100'),
  768   => codeword('011001101'),
  832   => codeword('011010010'),
  896   => codeword('011010011'),
  960   => codeword('011010100'),
  1024  => codeword('011010101'),
  1088  => codeword('011010110'),
  1152  => codeword('011010111'),
  1216  => codeword('011011000'),
  1280  => codeword('011011001'),
  1344  => codeword('011011010'),
  1408  => codeword('011011011'),
  1472  => codeword('010011000'),
  1536  => codeword('010011001'),
  1600  => codeword('010011010'),
  1664  => codeword('011000'),
  1728  => codeword('010011011'),

  1792  => codeword('00000001000'),
  1856  => codeword('00000001100'),
  1920  => codeword('00000001001'),
  1984  => codeword('000000010010'),
  2048  => codeword('000000010011'),
  2112  => codeword('000000010100'),
  2176  => codeword('000000010101'),
  2240  => codeword('000000010110'),
  2340  => codeword('000000010111'),
  2368  => codeword('000000011100'),
  2432  => codeword('000000011101'),
  2496  => codeword('000000011110'),
  2560  => codeword('000000011111')
}
WHITE_CONFIGURATION_DECODE_TABLE = 
WHITE_CONFIGURATION_ENCODE_TABLE.invert
BLACK_CONFIGURATION_ENCODE_TABLE = 
{
  64    => codeword('0000001111'),
  128   => codeword('000011001000'),
  192   => codeword('000011001001'),
  256   => codeword('000001011011'),
  320   => codeword('000000110011'),
  384   => codeword('000000110100'),
  448   => codeword('000000110101'),
  512   => codeword('0000001101100'),
  576   => codeword('0000001101101'),
  640   => codeword('0000001001010'),
  704   => codeword('0000001001011'),
  768   => codeword('0000001001100'),
  832   => codeword('0000001001101'),
  896   => codeword('0000001110010'),
  960   => codeword('0000001110011'),
  1024  => codeword('0000001110100'),
  1088  => codeword('0000001110101'),
  1152  => codeword('0000001110110'),
  1216  => codeword('0000001110111'),
  1280  => codeword('0000001010010'),
  1344  => codeword('0000001010011'),
  1408  => codeword('0000001010100'),
  1472  => codeword('0000001010101'),
  1536  => codeword('0000001011010'),
  1600  => codeword('0000001011011'),
  1664  => codeword('0000001100100'),
  1728  => codeword('0000001100101'),
  
  1792  => codeword('00000001000'),
  1856  => codeword('00000001100'),
  1920  => codeword('00000001001'),
  1984  => codeword('000000010010'),
  2048  => codeword('000000010011'),
  2112  => codeword('000000010100'),
  2176  => codeword('000000010101'),
  2240  => codeword('000000010110'),
  2340  => codeword('000000010111'),
  2368  => codeword('000000011100'),
  2432  => codeword('000000011101'),
  2496  => codeword('000000011110'),
  2560  => codeword('000000011111')
}
BLACK_CONFIGURATION_DECODE_TABLE = 
BLACK_CONFIGURATION_ENCODE_TABLE.invert

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(parameters = {}) ⇒ CCITTFax

Creates a new CCITT Fax Filter.



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# File 'lib/origami/filters/ccitt.rb', line 295

def initialize(parameters = {})
  super(DecodeParms.new(parameters))  
end

Class Method Details

.codeword(str) ⇒ Object

:nodoc:



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# File 'lib/origami/filters/ccitt.rb', line 55

def self.codeword(str) #:nodoc:
  [ str.to_i(2), str.length ]
end

Instance Method Details

#decode(stream) ⇒ Object

Decodes data using CCITT-facsimile compression method.



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# File 'lib/origami/filters/ccitt.rb', line 365

def decode(stream)
  if @params.has_key?(:K) and @params.K != 0
    raise NotImplementedError, "CCITT encoding scheme not supported"
  end

  columns = @params.has_key?(:Columns) ? @params.Columns.value : 1728
  unless columns.is_a?(::Integer) and columns > 0 and columns % 8 == 0
    raise CCITTFaxFilterError, "Invalid value for parameter `Columns'"
  end

  white, black = (@params.BlackIs1 == true) ? [0,1] : [1,0]
  aligned = @params.EncodedByteAlign == true
  has_eob = @params.EndOfBlock.nil? or @params.EndOfBlock == true
  has_eol = @params.EndOfLine == true

  unless has_eob
    unless @params.has_key?(:Rows) and @params.Rows.is_a?(::Integer) and @params.Rows.value > 0
      raise CCITTFaxFilterError, "Invalid value for parameter `Rows'"
    end

    rows = @params.Rows.to_i
  end

  bitr = Utils::BitReader.new(stream)
  bitw = Utils::BitWriter.new

  current_color = white
  until bitr.eod? or rows == 0
    
    # realign the read line on a 8-bit boundary if required
    if aligned and bitr.pos % 8 != 0
      bitr.pos += 8 - (bitr.pos % 8)          
    end

    # received return-to-control code 
    if has_eob and bitr.peek(RTC[1]) == RTC[0]
      bitr.pos += RTC[1]
      break
    end

    # checking for the presence of EOL
    if bitr.peek(EOL[1]) != EOL[0]
      raise CCITTFaxFilterError, "No end-of-line pattern found (at bit pos #{bitr.pos}/#{bitr.size}})" if has_eol
    else
      bitr.pos += EOL[1]
    end

    line_length = 0
    while line_length < columns
      if current_color == white
        bit_length = get_white_bits(bitr)
      else
        bit_length = get_black_bits(bitr)
      end

      raise CCITTFaxFilterError, "Unfinished line (at bit pos #{bitr.pos}/#{bitr.size}})" if bit_length.nil?
      
      line_length += bit_length
      raise CCITTFaxFilterError, "Line is too long (at bit pos #{bitr.pos}/#{bitr.size}})" if line_length > columns

      write_bit_range(bitw, current_color, bit_length)
      current_color ^= 1
    end

    rows -= 1 unless has_eob
  end

  bitw.final.to_s
end

#encode(stream) ⇒ Object

Encodes data using CCITT-facsimile compression method.



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# File 'lib/origami/filters/ccitt.rb', line 302

def encode(stream)

  if @params.has_key?(:K) and @params.K != 0
    raise NotImplementedError, "CCITT encoding scheme not supported"
  end

  columns = @params.has_key?(:Columns) ? @params.Columns.value : (stream.size << 3)
  unless columns.is_a?(::Integer) and columns > 0 and columns % 8 == 0
    raise CCITTFaxFilterError, "Invalid value for parameter `Columns'"
  end

  if stream.size % (columns >> 3) != 0
    raise CCITTFaxFilterError, "Data size is not a multiple of image width"
  end

  white, black = (@params.BlackIs1 == true) ? [0,1] : [1,0]

  bitr = Utils::BitReader.new(stream)
  bitw = Utils::BitWriter.new

  until bitr.eod?
    
    bitw.write(*EOL)
    scan_len = 0
    current_color = white

    # Process each bit in line.
    begin
      if bitr.read(1) == current_color
        scan_len += 1
      else
        if current_color == white
          put_white_bits(bitw, scan_len)
        else
          put_black_bits(bitw, scan_len)
        end

        current_color ^= 1
        scan_len = 1
      end
    end while bitr.pos % columns != 0

    if current_color == white
      put_white_bits(bitw, scan_len)
    else
      put_black_bits(bitw, scan_len)
    end

    # Align encoded lign on a 8-bit boundary.
    if @params.EncodedByteAlign == true and bitw.pos % 8 != 0
      bitw.write(0, 8 - (bitw.pos % 8))
    end
  end

  # Emit return-to-control code
  bitw.write(*RTC)

  bitw.final.to_s
end