Class: Origami::Filter::CCITTFax

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

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

    1792  => '00000001000',
    1856  => '00000001100',
    1920  => '00000001001',
    1984  => '000000010010',
    2048  => '000000010011',
    2112  => '000000010100',
    2176  => '000000010101',
    2240  => '000000010110',
    2340  => '000000010111',
    2368  => '000000011100',
    2432  => '000000011101',
    2496  => '000000011110',
    2560  => '000000011111'
}.map {|length, bits| [length, codeword(bits)]}.to_h
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.



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# File 'lib/origami/filters/ccitt.rb', line 58

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

Class Method Details

.codeword(str) ⇒ Object

:nodoc:



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# File 'lib/origami/filters/ccitt/tables.rb', line 27

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 117

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

    unless mode.is_a?(::Integer) and mode <= 0
        raise NotImplementedError.new("CCITT encoding scheme not supported", input_data: stream)
    end

    columns = @params.has_key?(:Columns) ? @params.Columns.value : 1728
    unless columns.is_a?(::Integer) and columns >= 0
        raise CCITTFaxFilterError.new("Invalid value for parameter `Columns'", input_data: stream)
    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?]
        rows = @params.key?(:Rows) ? @params.Rows.value : 0

        unless rows.is_a?(::Integer) and rows >= 0
            raise CCITTFaxFilterError.new("Invalid value for parameter `Rows'", input_data: stream)
        end
    end

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

    # Group 4 requires an imaginary white line
    if columns > 0 and 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

        break if columns == 0

        # 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}})",
                    input_data: stream,
                    decoded_data: bitw.final.to_s
            ) if params[:has_eol?]
        else
            bitr.pos += EOL[1]
        end

        begin
            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
        rescue DecodeError => error
            error.input_data = stream
            error.decoded_data = bitw.final.to_s

            raise error
        end

        rows -= 1 unless params[: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 65

def encode(stream)
    mode = @params.key?(:K) ? @params.K.value : 0
    colors = (@params.BlackIs1 == true) ? [0,1] : [1,0]
    use_eob = (@params.EndOfBlock.nil? or @params.EndOfBlock == true)
    use_eol = (@params.EndOfLine == true)
    white, _black = colors

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

    unless mode.is_a?(::Integer) and mode <= 0
        raise NotImplementedError.new("CCITT encoding scheme not supported", input_data: stream)
    end

    # Use a single row if no width has been set.
    @params[:Columns] ||= stream.size * 8
    columns = @params.Columns.value

    unless columns.is_a?(::Integer) and columns >= 0
        raise CCITTFaxFilterError.new("Invalid value for parameter `Columns'", input_data: stream)
    end

    if columns > 0
        # 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?
            # Emit line synchronization code.
            bitw.write(*EOL) if use_eol

            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
    end

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

    bitw.final.to_s
end