extend.m

一个简单的图象去噪的算法

function  Ae=extend(A, flag)
% extend.m  extends  data  across  the   boundaries (to make other codes
%           uniform and simple).
% Input : A is an nxmxk array.  
% Output: an expanded image (across four boundary edges)
%         if flag ==1,  do Nuemann extension (zero derivative). 
%         if flag ~=1,  do zero extension. 
d=length(size(A));            % so d is the dimension of A.            
										% d=2 means a one-channel 2-D image
                              % d=3 means at least 2-channel 2-D image.
if d==2                       %%%  so  A is a grey-leve image.
 [n, m]= size(A);
 %  define the interior of the extended.
 Ae(2:n+1, 2:m+1)=A;             
 if flag==1,                    %  Nuemann extension 
 % the four boundary edges
 Ae(1, 2:m+1)=A(1,:);
 Ae(n+2, 2:m+1)=A(n, :);
 Ae(2:n+1, 1)=A(:, 1);
 Ae(2:n+1, m+2)=A(:, m);
 % the four  corners
 Ae(1, 1)=A(1, 1);
 Ae(1, m+2)=A(1, m);
 Ae(n+2, 1)=A(n, 1);
 Ae(n+2, m+2)=A(n, m);
else                           %  zero extension
 % the four boundary edges
 hz = zeros(1, m);
 vz = zeros(n, 1);
 Ae(1, 2:m+1)=hz;
 Ae(n+2, 2:m+1)=hz;
 Ae(2:n+1, 1)=vz;
 Ae(2:n+1, m+2)=vz; 

 % the four corners
 Ae(1, 1)=0;
 Ae(1, m+2)=0;
 Ae(n+2, 1)=0;
 Ae(n+2, m+2)=0;
end
else                                % so d=3 -- 3-dimension. 

 [n, m, k]=size(A);                 %  k=3 or 2 in our applications.
 
 %  define the interior
 Ae(2:n+1, 2:m+1, :)=A;            

 if flag==1,                        %  Nuemann extension 

 % the four boundary edges
 Ae(1, 2:m+1, :)  =A(1, :, :);
 Ae(n+2, 2:m+1, :)=A(n, :, :);
 Ae(2:n+1, 1, :)  =A(:, 1, :);
 Ae(2:n+1, m+2, :)=A(:, m, :);

 % the four corners
 Ae( 1, 1, :)    =A( 1, 1, :);
 Ae( 1, m+2, :)  =A( 1, m, :);
 Ae( n+2, 1, :)  =A( n, 1, :);
 Ae( n+2, m+2, :)=A( n, m, :);

 else                               %  Zero extension
 % the four boundary edges
 hz = zeros(1, m, k);
 vz = zeros(n, 1, k);
 Ae( 1, 2:m+1, :)   =hz;
 Ae( n+2, 2:m+1, :) =hz;
 Ae( 2:n+1, 1, :)   =vz;
 Ae( 2:n+1, m+2, :) =vz; 
 % the four corners
 corner=zeros(1, 1, k);
 Ae( 1, 1, :)    =corner;
 Ae( 1, m+2, :)  =corner;
 Ae( n+2, 1, :)  =corner;
 Ae( n+2, m+2, :)=corner;
end
end