Help on how to achieve lossless image compression using arithmetic encoding and decoding.

Question

enyawson 2023-9-18

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https://ww2.mathworks.cn/matlabcentral/answers/2022607-help-on-how-to-achieve-lossless-image-compression-using-arithmetic-encoding-and-decoding

编辑： enyawson 2023-9-18

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Had this error after passing the coefficients of wavelet image tranform, symbols and probability to the package

Arithmetic Encoding & Decoding

Version 1.0.0.0 (2.67 KB) by Vinay Kumar Tadepalli

Error:

[Tag_bits]= Arithmetic_enc(sym,p,c);

Plese enter proper values!!!

Elapsed time is 0.000439 seconds.

Output argument "Tag_bits" (and possibly others) not assigned a value in the execution with "Arithmetic_enc" function.

code:

function Tag_bits =Arithmetic_enc(sym,p,seq)
tic;  % TIC-TOC commands are used to measure the simulation time of the program.
format long g;
%% ARGUMENTS OF THE FUNCTION
% SYM is a string of symbols of information from the source.
% P represents the array of Probabilities of the corresponding symbols in
% the SYM string.
% SEQ is the string of sequence of symbols to be encoded by arithmetic
% coding.
if(length(sym)==length(p) && sum(p)==1)  
    %% ALGORITHM IMPLEMENTATION
    
    % Calculate the Symbol Intervals.
    Fx=zeros(1,length(sym));
    for i=1:length(sym)
        if i==1
            Fx(i)=p(i);
        else
            Fx(i)=Fx(i-1)+p(i);
        end
    end
    
    % Encoding the Sequence of Symbols. 
    L=0;U=1; % Initial Lower and Upper Intervals.
    Tag_bits=zeros(1,0); % Initializing the Tag Bits.
    for i=1:length(seq)
        j=find(seq(i)==sym);   % Finds the Index of the sequence symbol in the symbol string.
        if(j==1)
            L_new=L;
        else
            L_new=L+(U-L)*Fx(j-1);
        end
        U_new=L+(U-L)*Fx(j);
        L=L_new;
        U=U_new;
        while((L<0.5 && U<0.5) ||(L>=0.5 && U>0.5))
            if(L<0.5 && U<0.5)
                Tag_bits=[Tag_bits,'0'];
                L=2*L;
                U=2*U;
            else
                Tag_bits=[Tag_bits,'1'];
                L=2*(L-0.5);
                U=2*(U-0.5);
            end
        end
    end
    tag=(L+U)/2;
    
    % Embedding the Final Tag Value.
    bits=zeros(1,0);
    if(2*tag>1)
        tag=2*tag-1;
        bits=[bits,'1'];
    else
        tag=2*tag;
        bits=[bits,'0'];
    end
    while(bin2dec(bits)/2^length(bits)<L)
        if(2*tag>1)
            tag=2*tag-1;
            bits=[bits,'1'];
        else
            tag=2*tag;
            bits=[bits,'0'];
        end
    end
    Tag_bits=[Tag_bits,bits];
    
    % Padding of zeros is done to keep the TAG BITS size multiple of 16 bits.
    Tag_bits=[Tag_bits,dec2bin(0,16-rem(length(Tag_bits),16))];
    display('Tag Value is:');
    disp(bin2dec(Tag_bits)/2^length(Tag_bits));
    display('Tag Word is:');
    Tag_bits=[Tag_bits,dec2bin(length(seq),16)];
else
    display('Plese enter proper values!!!');
end
toc;

workspace values for

seq = c

c= 1x349184 double

p = 1x349118 double

sym = 1x349118 double

sum(p)

ans = 0.999999999999999

Help on how to achieve lossless image compression with any other package or this package for arithmetic encoding and decoding.

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DGM 2023-9-18

编辑：DGM 2023-9-18

Since we don't know how you tried to call the function, we don't know whether any other suggestion would work either. All we know is that one of the following is true: