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

Constants included from Origami::Filter

A85, AHx, CCF, Fl, RL

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Origami::Filter

included

Constructor Details

#initialize(parameters = {}) ⇒ CCITTFax

Creates a new CCITT Fax Filter.



295
296
297
 
# File 'lib/origami/filters/ccitt.rb', line 295

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

Class Method Details

.codeword(str) ⇒ Object

:nodoc:



55
56
57
 
# 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.



348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
 
# File 'lib/origami/filters/ccitt.rb', line 348

def decode(stream)
  mode = @params.has_key?(:K) ? @params.K.value : 0 

  unless mode.is_a?(::Integer) and mode <= 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

  colors = (@params.BlackIs1 == true) ? [0,1] : [1,0]
  white, _black = colors
  params = 
  {
    :is_aligned? => (@params.EncodedByteAlign == true),
    :has_eob? => (@params.EndOfBlock.nil? or @params.EndOfBlock == true),
    :has_eol? => (@params.EndOfLine == true)
  }

  unless params[: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

  # Group 4 requires an imaginary white line
  if mode < 0
    prev_line = Utils::BitWriter.new
    write_bit_range(prev_line, white, columns)
    prev_line = Utils::BitReader.new(prev_line.final.to_s)
  end

  until bitr.eod? or rows == 0
    # realign the read line on a 8-bit boundary if required
    if params[:is_aligned?] and bitr.pos % 8 != 0
      bitr.pos += 8 - (bitr.pos % 8)          
    end

    # received return-to-control code 
    if params[: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 InvalidCCITTFaxDataError.new(
        "No end-of-line pattern found (at bit pos #{bitr.pos}/#{bitr.size}})",
        bitw.final.to_s
      ) if params[:has_eol?]
    else
      bitr.pos += EOL[1]
    end

    case
      when mode == 0
        decode_one_dimensional_line(bitr, bitw, columns, colors)
      when mode < 0
        decode_two_dimensional_line(bitr, bitw, columns, colors, prev_line)
    end 


    rows -= 1 unless params[:has_eob?]
  end

  bitw.final.to_s
end

#encode(stream) ⇒ Object

Encodes data using CCITT-facsimile compression method.



302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
 
# File 'lib/origami/filters/ccitt.rb', line 302

def encode(stream)
  mode = @params.has_key?(:K) ? @params.K.value : 0 

  unless mode.is_a?(::Integer) and mode <= 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

  colors = (@params.BlackIs1 == true) ? [0,1] : [1,0]
  white, _black = colors
  bitr = Utils::BitReader.new(stream)
  bitw = Utils::BitWriter.new

  # Group 4 requires an imaginary white line
  if mode < 0
    prev_line = Utils::BitWriter.new
    write_bit_range(prev_line, white, columns)
    prev_line = Utils::BitReader.new(prev_line.final.to_s)
  end

  until bitr.eod?
    case
      when mode == 0
        encode_one_dimensional_line(bitr, bitw, columns, colors)  
      when mode < 0
        encode_two_dimensional_line(bitr, bitw, columns, colors, prev_line)
    end
  end

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

  bitw.final.to_s
end