LZW compression using easy method(Dictionary-based coding)in DIP & Implementation in MATLAB in Hindi

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  • Опубликовано: 14 дек 2024

Комментарии • 6

  • @StudywithDrDafda
    @StudywithDrDafda  2 года назад

    function [output,table, Alphabet] = LZW_encoder_string(vector)
    % LZW Data Compression for string (encoder)
    % For vectors, LZW_encoder_string(X) is the compressed vector
    % of X using the LZW algorithm.
    % [...,T] = LZW_encoder_string(X) returns also the table
    % that the algorithm produces.
    % For matrices, X(:) is used as fprintf.
    % fprintf must be of uint8 type, while the output is a uint16.
    %Table is a cell array, each element_k containing the resp.code.
    % How it encodes:
    % STRING = get fprintf character
    % WHILE there are still fprintf characters DO
    % CHARACTER = get fprintf character
    % IF STRING+CHARACTER is in the string table then
    % STRING = STRING+character
    % ELSE
    % output the code for STRING
    % add STRING+CHARACTER to the string table
    % STRING = CHARACTER
    % END of IF
    % END of WHILE
    % output the code for STRING
    % ensure to handle uint8 fprintf vector
    if ~isa(vector,'uint8'),
    error('fprintf argument must be a uint8 vector')
    end
    % vector as uint16 row
    vector = uint16(vector(:)');
    %initialize table (don't use cellstr because char(10) will be turned to empty!!!)
    fprintf('Initialising Table
    ');
    table = [];
    Alphabet = unique(vector);
    for i = 1:numel(Alphabet)
    [table, code] = addcode(table, (double(Alphabet(i))));
    fprintf('Table Entry %d : %s
    ', i, char(Alphabet(i)));
    end
    fprintf('
    ');
    % initialize output
    output = vector;
    % main loop
    outputindex = 1;
    startindex = 1;
    element_k = vector(1);
    substr_w = [];
    fprintf('w k output index symbol
    ');
    fprintf('------------------------------------
    ');
    fprintf('NIL\t\t%s
    ', char(element_k));

    for index=2:length(vector),
    element_k = vector(index);
    substr_w = vector(startindex:(index-1));
    code = getcodefor([substr_w element_k],table);

    if isempty(code),
    % add it to the table
    output(outputindex) = getcodefor(substr_w,table);
    [table,code] = addcode(table,[substr_w element_k]);
    fprintf('%s\t\t%s\t\t%d\t\t%d\t\t%s
    ', ...
    char(substr_w), char(element_k), output(outputindex), code,...
    char([substr_w element_k]));
    outputindex = outputindex+1;
    startindex = index;
    else
    fprintf('%s\t\t%s
    ', char(substr_w), char(element_k));
    end
    end
    substr_w = vector(startindex:index);
    output(outputindex) = getcodefor(substr_w,table);
    % remove not used positions
    output((outputindex+1):end) = [];
    % ###############################################
    function code = getcodefor(substr,table)
    code = uint16([]);
    for index=1:length(table),
    if isequal(substr,table{index}),
    code = uint16(index); % start from 0
    break
    end
    end
    % ###############################################
    function [table,code] = addcode(table,substr_w)
    code = length(table)+1; % start from 1
    table{code} = substr_w;
    code = uint16(code); % start from 1

  • @StudywithDrDafda
    @StudywithDrDafda  2 года назад

    function [output,table] = LZW_decoder_image(vector, alphabet)
    % LZW Data Compression (decoder)
    % For vectors, LZW_decoder_image(X) is the uncompressed
    % vector of X using the LZW algorithm.
    % [...,T] = LZW_decoder_image(X) returns also the table
    % that the algorithm produces.
    % For matrices, X(:) is used as input.
    % Input must be of uint16 type, while the output_w is a uint8.
    %Table is a cell array, each element_k containing the resp. code.
    % How it decodes:
    % Read OLD_CODE
    % output_w OLD_CODE
    % CHARACTER = OLD_CODE
    % WHILE there are still input characters DO
    % Read NEW_CODE
    % IF NEW_CODE is not in the translation table THEN
    % entry = get translation of OLD_CODE
    % entry = entry+CHARACTER
    % ELSE
    % entry = get translation of NEW_CODE
    % END of IF
    % output_w entry
    % CHARACTER = first character in entry
    %add translation of OLD_CODE + CHARACTER to the translation table
    % OLD_CODE = NEW_CODE
    % END of WHILE
    % ensure to handle uint8 input vector
    if ~isa(vector,'uint16'),
    error('input argument must be a uint16 vector')
    end
    % vector as a row
    vector = vector(:)';
    %Intialise Table
    fprintf('Initialising Table
    ');
    table = [];
    % Alphabet = unique(vector);
    for i = 1:numel(alphabet)
    [table,code] = addcode(table, uint16(double(i)));
    end
    for index = 1:numel(table),
    fprintf('Table Entry %d: %d
    ',index, alphabet(table{index}));
    end
    fprintf('
    ');
    % initialize output_w
    output = uint8([]);
    code = vector(1);
    output(end+1) = table{code};
    character = code;
    fprintf('Input + code_w k (w=k): %d
    ', code);
    fprintf('w k output index symbol
    ');
    fprintf('------------------------------------
    ');
    fprintf('NIL\t\t%d
    ', alphabet(code));

    for index=2:length(vector),
    element_k = vector(index);
    %k_pos = getcodefor(element_k,table)
    % fprintf('Input k: %d
    ', code);
    % element_k
    if (element_k)>length(table),
    % add it to the table
    entry = table{double(code)};
    entry = [entry character];
    else
    entry = element_k;
    end

    if code > numel(alphabet)
    ow = num2str(code);
    else
    ow = alphabet(code);
    end

    if element_k > numel(alphabet)
    ok = num2str(element_k);
    else
    ok = alphabet(element_k);
    end


    character = table{entry};
    [table,code] = addcode(table,[table{code} character(1)]);
    fprintf('%d\t\t%d\t\t%d\t\t%d\t\t%d
    ',ow,ok,char(alphabet(table{entry})),...
    code, alphabet([table{code}]));
    warning off
    output = [output table{entry}];
    warning on
    code = element_k;
    end
    % ###############################################
    function code = getcodefor(substr,table)
    code = uint16([]);
    for index=1:length(table),
    if isequal(substr,table{index}),
    code = uint16(index); % start from 0
    break
    end
    end
    % ###############################################
    function [table,code] = addcode(table,substr)
    code = length(table)+1; % start from 1
    table{code} = substr;
    code = uint16(code); % start from 1

  • @unmeshdhere1263
    @unmeshdhere1263 Год назад

    It's says error in line 9
    Unrecognised function or variable ... 'LZW_encoder_string'.

    • @StudywithDrDafda
      @StudywithDrDafda  Год назад

      Save the functions written in comments in MATLAB folder and then run the program. The program uses these functions.

  • @StudywithDrDafda
    @StudywithDrDafda  2 года назад

    function [output,table] = LZW_decoder_string(vector, alphabet)
    % LZW Data Compression for string(decoder)
    % For vectors, LZW_decoder_string(X) is the uncompressed
    % vector of X using the LZW algorithm.
    % [...,T] = LZW_decoder_string(X) returns also the table
    % that the algorithm produces.
    % For matrices, X(:) is used as input.
    % Input must be of uint16 type, while the output_w is a uint8.
    %Table is a cell array, each element_k containing the resp.code.
    % How it decodes:
    % Read OLD_CODE
    % output_w OLD_CODE
    % CHARACTER = OLD_CODE
    % WHILE there are still input characters DO
    % Read NEW_CODE
    % IF NEW_CODE is not in the translation table THEN
    % entry = get translation of OLD_CODE
    % entry = entry+CHARACTER
    % ELSE
    % entry = get translation of NEW_CODE
    % END of IF
    % output_w entry
    % CHARACTER = first character in entry
    %add translation of OLD_CODE + CHARACTER to the translation table
    % OLD_CODE = NEW_CODE
    % END of WHILE
    % ensure to handle uint8 input vector
    if ~isa(vector,'uint16'),
    error('input argument must be a uint16 vector')
    end
    % vector as a row
    vector = vector(:)';
    %Intialise Table
    fprintf('Initialising Table
    ');
    table = [];
    % Alphabet = unique(vector);
    for i = 1:numel(alphabet)
    [table,code] = addcode(table, uint16(double(i)));
    end
    for index = 1:numel(table),
    fprintf('Table Entry %d : %s
    ',index, alphabet(table{index}));
    end
    % initialize output_w
    output = uint8([]);
    code = vector(1);
    output(end+1) = table{code};
    character = code;
    fprintf('Input + code_w k (w=k): %d
    ', code);
    fprintf('w k output index symbol
    ');
    fprintf('------------------------------------
    ');
    fprintf('NIL\t\t%s
    ', alphabet(code));
    for index=2:length(vector),
    element_k = vector(index);
    %k_pos = getcodefor(element_k,table)
    % fprintf('Input k: %d
    ', code);
    % element_k
    if (element_k)>length(table),
    % add it to the table
    entry = table{double(code)};
    entry = [entry character];
    else
    entry = element_k;
    end

    if code > numel(alphabet)
    ow = num2str(code);
    else
    ow = alphabet(code);
    end

    if element_k > numel(alphabet)
    ok = num2str(element_k);
    else
    ok = alphabet(element_k);
    end
    character = table{entry};
    [table,code] = addcode(table,[table{code} character(1)]);
    fprintf('%s\t\t%s\t\t%s\t\t%d\t\t%s', ow, ok, char(alphabet(table{entry})), ...
    code, alphabet([table{code}]));
    warning off
    output = [output table{entry}];
    warning on
    code = element_k;
    end
    % ###############################################
    function code = getcodefor(substr,table)
    code = uint16([]);
    for index=1:length(table),
    if isequal(substr,table{index}),
    code = uint16(index); % start from 0
    break
    end
    end
    % ###############################################
    function [table,code] = addcode(table,substr)
    code = length(table)+1; % start from 1
    table{code} = substr;
    code = uint16(code); % start from 1

  • @StudywithDrDafda
    @StudywithDrDafda  2 года назад

    function [output,table, Alphabet] = LZW_encoder_image(vector)
    % LZW Data Compression (encoder)
    % For vectors, LZW_encoder_image(X) is the compressed vector
    % of X using the LZW algorithm.
    % [...,T] = LZW_encoder_image(X) returns also the table
    % that the algorithm produces.
    % For matrices, X(:) is used as fprintf.
    % fprintf must be of uint8 type, while the output is a uint16.
    % Table is a cell array, each element_k containing resp.code.
    % How it encodes:
    % STRING = get fprintf character
    % WHILE there are still fprintf characters DO
    % CHARACTER = get fprintf character
    % IF STRING+CHARACTER is in the string table then
    % STRING = STRING+character
    % ELSE
    % output the code for STRING
    % add STRING+CHARACTER to the string table
    % STRING = CHARACTER
    % END of IF
    % END of WHILE
    % output the code for STRING
    % ensure to handle uint8 fprintf vector
    if ~isa(vector,'uint8'),
    error('fprintf argument must be a uint8 vector')
    end
    % vector as uint16 row
    vector = uint16(vector(:)');
    % initialize table (don't use cellstr because char(10)
    % will be turned to empty!!!)
    fprintf('Initialising Table
    ');
    table = [];
    Alphabet = unique(vector);
    for i = 1:numel(Alphabet)
    [table, code] = addcode(table, (double(Alphabet(i))));
    fprintf('Table Entry %d : %d
    ', i, char(Alphabet(i)));
    end
    fprintf('
    ');
    % initialize output
    output = vector;
    % main loop
    outputindex = 1;
    startindex = 1;
    element_k = vector(1);
    substr_w = [];
    fprintf('w k output index symbol
    ');
    fprintf('------------------------------------
    ');
    fprintf('NIL\t\t%d
    ', char(element_k));

    for index=2:length(vector)
    element_k = vector(index);
    substr_w = vector(startindex:(index-1));
    code = getcodefor([substr_w element_k],table);

    if isempty(code)
    % add it to the table
    output(outputindex) = getcodefor(substr_w,table);
    [table,code] = addcode(table,[substr_w element_k]);
    fprintf('%d\t\t%d\t\t%d\t\t%d\t\t%d
    ',...
    char(substr_w), char(element_k), output(outputindex), code, ...
    char([substr_w element_k]));
    outputindex = outputindex+1;
    startindex = index;
    else
    % go on looping
    fprintf('%d\t\t%d
    ', char(substr_w), char(element_k));
    end
    end
    substr_w = vector(startindex:index);
    output(outputindex) = getcodefor(substr_w,table);
    % remove not used positions
    output((outputindex+1):end) = [];
    % ###############################################
    function code = getcodefor(substr,table)
    code = uint16([]);
    for index=1:length(table),
    if isequal(substr,table{index}),
    code = uint16(index); % start from 0
    break
    end
    end
    % ###############################################
    function [table,code] = addcode(table,substr_w)
    code = length(table)+1; % start from 1
    table{code} = substr_w;
    code = uint16(code); % start from 1