mainpass.m

ezw编码

function [D,X,sublist,sub_list] = mainpass(X,threshold,sublist,sub_list) 
%主扫描程序
D=[];
global N;
global C;
[m,n]=size(X);
R=zeros(m); % matrix R is a reference matrix, same size as X; '0' means
            %this coefficient is not a descendant from zerotree root;
            %R矩阵与X同样大小，用于标识是否为子孙系数，‘0’为非

[a,b]=size(N);
         if C(1,1)==0     
             if abs(X(1,1))>=threshold % X(1,1) is DC coefficient
                 sublist=[sublist, abs(X(1,1))]; %在sublist中存放重要系数的数据
                 sub_list=[sub_list;N(1,1),N(1,2)];%在sub_list中存放重要系数的坐标
                  C(1,1)=1;
                  if X(1,1)>0
                      D=[D,'p']; 
                  else D=[D,'n'];
                  end
                  X(1,1)=0;
             else
                 D=[D,'z'];
             end
         end
         for k=2:4,
          if C(N(k,1),N(k,2))==0
              if abs(X(N(k,1),N(k,2)))>=threshold
                  sublist=[sublist, abs(X(N(k,1),N(k,2)))]; % 扩充存放重要系数;
                  sub_list=[sub_list;N(k,1),N(k,2)];
                  C(N(k,1),N(k,2))=1;
                                 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;%在小波系数矩阵中，所有重要系数都被标为0  
              else
                                 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
         end
          for k=5:a,
               if C(N(k,1),N(k,2))==0
                   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)];
                       C(N(k,1),N(k,2))=1;
                       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); %检查子孙系数中是否有重要系数             
                       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);
                           % 如果是零树，则将他所有的子孙系数在R矩阵中置0
                       end
                   end
               end
          end