www.pudn.com > ex5-5.rar > func_Myappcoef2.m

function a = func_Myappcoef2(c,s,varargin) 
%APPCOEF2 Extract 2-D approximation coefficients. 
%   APPCOEF2 computes the approximation coefficients of a 
%   two-dimensional signal. 
% 
%   A = APPCOEF2(C,S,'wname',N) computes the approximation 
%   coefficients at level N using the wavelet decomposition 
%   structure [C,S] (see WAVEDEC2).  
%   'wname' is a string containing the wavelet name. 
%   Level N must be an integer such that 0 <= N <= size(S,1)-2.  
% 
%   A = APPCOEF2(C,S,'wname') extracts the approximation 
%   coefficients at the last level size(S,1)-2. 
% 
%   Instead of giving the wavelet name, you can give the filters. 
%   For A = APPCOEF2(C,S,Lo_R,Hi_R) or  
%   A = APPCOEF2(C,S,Lo_R,Hi_R,N), 
%   Lo_R is the reconstruction low-pass filter and 
%   Hi_R is the reconstruction high-pass filter. 
%    
%   See also DETCOEF2, WAVEDEC2. 
 
%   M. Misiti, Y. Misiti, G. Oppenheim, J.M. Poggi 12-Mar-96. 
%   Last Revision: 02-Aug-2000. 
%   Copyright 1995-2002 The MathWorks, Inc. 
% $Revision: 1.12 $ 
 
% Check arguments. 
if errargn(mfilename,nargin,[3:5],nargout,[0:1]), error('*'), end 
rmax = size(s,1); 
nmax = rmax-2; 
if ischar(varargin{1}) 
    [Lo_R,Hi_R] = wfilters(varargin{1},'r'); next = 2; 
else 
    Lo_R = varargin{1}; Hi_R = varargin{2};  next = 3; 
end 
if nargin>=(2+next) , n = varargin{next}; else, n = nmax; end 
 
if (n<0) | (n>nmax) | (n~=fix(n)) 
    errargt(mfilename,'invalid level value','msg'); error('*'); 
end 
 
nl   = s(1,1); 
nc   = s(1,2); 
a    = zeros(nl,nc); 
a(:) = c(1:nl*nc); 
 
rm   = rmax+1; 
for p=nmax:-1:n+1 
    [h,v,d] = detcoef2('all',c,s,p); 
    a = idwt2(a,h,v,d,Lo_R,Hi_R,s(rm-p,:),'mode','per'); 
end