dominantpass.m

EZW法是一個用matlab寫的程式,是植基於小波的影像壓縮轉換

function [D,X,sublist,sub_list] = dominantpass(X,threshold,sublist,sub_list) 
% 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))]; % put significant coefficients's value to sublist
                  sub_list=[sub_list;N(1,1),N(1,2)];% put the significant coefficients' position in sub_list
                  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;
                    sub_list=[sub_list;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; 
      % 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;   % Zerotree, make all its descendants
                                     R=checkchildren(k,R); % refference matrix component to 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)))]; 
                      sub_list=[sub_list;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; 
                             
                   elseif R(N(k,1),N(k,2))==0
                       
                                 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;  
                                     R=checkchildren(k,R);
                                 % if zerotree, reference matrix coefficients=1
                                 end
                   end
                   
           end