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huffman.m in imageprocessing.rar

			
function CODE = huffman(p)
%HUFFMAN Builds a variable-length Huffman code for a symbol source.
%   CODE = HUFFMAN(P) returns a Huffman code as binary strings in
%   cell array CODE for input symbol probability vector P. Each word
%   in CODE corresponds to a symbol whose probability is at the
%   corresponding index of P. 
%
%   Based on huffman5 by Sean Danaher, University of Northumbria,
%   Newcastle UK. Available at the MATLAB Central File Exchange:
%   Category General DSP in Signal Processing and Communications. 

%   Copyright 2002-2004 R. C. Gonzalez, R. E. Woods, & S. L. Eddins
%   Digital Image Processing Using MATLAB, Prentice-Hall, 2004
%   $Revision: 1.5 $  $Date: 2003/10/26 18:37:16 $

% Check the input arguments for reasonableness.
error(nargchk(1, 1, nargin));
if (ndims(p) ~= 2) | (min(size(p)) > 1) | ~isreal(p) | ~isnumeric(p)
   error('P must be a real numeric vector.');     
end
   
% Global variable surviving all recursions of function 'makecode'
global CODE
CODE = cell(length(p), 1);  % Init the global cell array
                            
if length(p) > 1            % When more than one symbol ...
   p = p / sum(p);          % Normalize the input probabilities
   s = reduce(p);           % Do Huffman source symbol reductions
   makecode(s, []);         % Recursively generate the code
else  
   CODE = {'1'};            % Else, trivial one symbol case!
end;   

%------			

			...
			...
			... to be continued.

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