dominantpass.m

这是利用matlab所写的ezw影像压缩法

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;
              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; 
    % the significent coefficients is replaced by a '0' in the coefficients matrix  
               else
                  % 2,3,4 has no parents,just check its descendants.
                                 result = checkdescendants1( 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);
                   else   zerotree = checkancestors1( k,R,0);

               % check coefficient is descended from zerotree root?   
                        if zerotree==0, % Not descends from zerotree root
                                 result = checkdescendants1( 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