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POCreate image from Huffman code - Matlab
 

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    <p>I have a project about image compression in Matlab. So far i have successfully implemented Huffman encoding to the image which gives me a vector of binary codes. After that i run Huffman decoding and i get a vector which contains the elements of the image compressed. My problem is that i can find how is possible from this vector to reconstruct the image and create the image file.</p> <p>Any help would be grateful</p> <p><strong>Update</strong></p> <p>Based on Ben A. help i have made progress but i still have some issues. To be more exact. I have an image matrix. After finding unique symbols(elements) on this image matrix, i calculate the probabilities and then with this function:</p> <pre><code>function [h,L,H]=Huffman_code(p,opt) % Huffman code generator gives a Huffman code matrix h, % average codeword length L &amp; entropy H % for a source with probability vector p given as argin(1) zero_one=['0'; '1']; if nargin&gt;1&amp;&amp;opt&gt;0, zero_one=['1'; '0']; end if abs(sum(p)-1)&gt;1e-6 fprintf('\n The probabilities in p does not add up to 1!'); end M=length(p); N=M-1; p=p(:); % Make p a column vector h={zero_one(1),zero_one(2)}; if M&gt;2 pp(:,1)=p; for n=1:N % To sort in descending order [pp(1:M-n+1,n),o(1:M-n+1,n)]=sort(pp(1:M-n+1,n),1,'descend'); if n==1, ord0=o; end % Original descending order if M-n&gt;1, pp(1:M-n,n+1)=[pp(1:M-1-n,n); sum(pp(M-n:M-n+1,n))]; end end for n=N:-1:2 tmp=N-n+2; oi=o(1:tmp,n); for i=1:tmp, h1{oi(i)}=h{i}; end h=h1; h{tmp+1}=h{tmp}; h{tmp}=[h{tmp} zero_one(1)]; h{tmp+1}=[h{tmp+1} zero_one(2)]; end for i=1:length(ord0), h1{ord0(i)}=h{i}; end h=h1; end L=0; for n=1:M, L=L+p(n)*length(h{n}); end % Average codeword length H=-sum(p.*log2(p)); % Entropy by Eq.(9.1.4) </code></pre> <p>i calculate the huffman codes for the image.</p> <p>Now i use this function:</p> <pre><code>function coded_seq=source_coding(src,symbols,codewords) % Encode a data sequence src based on the given (symbols,codewords). no_of_symbols=length(symbols); coded_seq=[]; if length(codewords)&lt;no_of_symbols error('The number of codewords must equal that of symbols'); end for n=1:length(src) found=0; for i=1:no_of_symbols if src(n)==symbols(i), tmp=codewords{i}; found=1; break; end end if found==0, tmp='?'; end coded_seq=[coded_seq tmp]; end </code></pre> <p>where in src i put my image (matrix) and i get a coded sequence for my image.</p> <p>Last is this function:</p> <pre><code>function decoded_seq=source_decoding(coded_seq,h,symbols) % Decode a coded_seq based on the given (codewords,symbols). M=length(h); decoded_seq=[]; while ~isempty(coded_seq) lcs= length(coded_seq); found=0; for m=1:M codeword= h{m}; lc= length(codeword); if lcs&gt;=lc&amp;codeword==coded_seq(1:lc) symbol=symbols(m); found=1; break; end if found==0, symbol='?'; end end decoded_seq=[decoded_seq symbol]; coded_seq=coded_seq(lc+1:end); end </code></pre> <p>Which is used to decode the coded sequence. The problem is that finally as coded sequence i get a 1x400 matrix where i should get a 225x400 which is my image dimensions. Am i missing something? Maybe should i replace something because i have a matrix and not a number sequence (for which the code is written)?</p>
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