dominantpass.m

EZW implementation which will use wavelet transforms and do the compression decompression using EZW

function [D,X,sublist] = dominantpass(X,threshold,sublist) 
% Dominant pass function
D=[];
global N;
[m,n]=size(X);
% X is the coefficients matrix
R=zeros(m); 
% matrix R is a reference matrix, same size as X; '0' means this coefficient is not a descendant from zerotree root;
[a,b]=size(N);
if abs(X(1,1))>=threshold; % X(1,1) is DC coefficient
    sublist=[sublist, abs(X(1,1))];
    if   X(1,1)>0;
         D=[D,'p'];
    else D=[D,'n'];
    end  
    X(1,1)=0;%标注
else D=[D,'z'];
end 
for k=2:4
    if  abs(X(N(k,1),N(k,2)))>=threshold,
        sublist=[sublist, abs(X(N(k,1),N(k,2)))];   % append this significant coefficient to the subordinate list;
        if   X(N(k,1),N(k,2))>0, % determine the sign
             D=[D,'p']; % >0,assign a "p"
        else D=[D,'n'];% <0,assign a "n"
        end
        X(N(k,1),N(k,2))=0; %标注 
    else
    % 2,3,4 has no parents,just check its descendants.
        result = checkdescendants( k,X,threshold,0);
        if   result==1,
             D=[D,'z'];
        else D=[D,'t'];
        R(N(k,1),N(k,2))=1; 
        end    
    end
end
for k=5:a,
    if  abs(X(N(k,1),N(k,2)))>=threshold, 
        sublist=[sublist, abs(X(N(k,1),N(k,2)))]; 
        if   X(N(k,1),N(k,2))>0, % determine the sign
             D=[D,'p']; % >0,assign a "p"
        else D=[D,'n'];% <0,assign a "n"
        end
        X(N(k,1),N(k,2))=0; 
    else   
        zerotree = checkancestors( k,R,0); % check coefficient is descended from zerotree root?   
        if  zerotree==0, % Not descends from zerotree root
            result = checkdescendants( k,X,threshold,0); % Check its has significant descendants? 
            if   result==1,
                 D=[D,'z']; % isolated zero
            else D=[D,'t'];% zerotree
            R(N(k,1),N(k,2))=1;% if zerotree, reference matrix coefficient=1
            end
        end  
    end
end