syntw2d.m

这是伯克里wavelet transforms一书中的例子的代码

function sy =  syntw2d(an,sl,sh,levs)
%Routine to reconstruct the 2-D signal from its multilevel DWT, using 
%an odd length or whole sample symmetric (WSS) separable biorthogonal 
%filter bank. Symmetric extension used to extend the subbands. This is 
%complemetary function to the analysis routine 'analw2d'.
%
%sy = syntw2d(an,lpf,hpf,L) reconstructs a 2-D image from its DWT, 'an',
%which could be the output of the routine 'analw2d'.
%The image is assumed to be decomposed to L levels. The WSS filter 
%bank used comprises of sl and sh. If this corresponds to the 
%analysis filter bank used for decomposition then you get perfect 
%reconstruction. The reconstructed image is returned as a 2-D array,
%sy.
%
%sy = syntw2d(an,fopt,L) reconstructs a 2-D array from its DWT, 'an',
%which could be the output of the routine 'analw2d'.
%The image is assumed to be decomposed to L levels. fopt chooses a
%WSS synthesis filter bank provided in the routine. If this corresponds
%to the analysis filter bank used for the decomposition then you get 
%perfect reconstruction. The reconstructed image is returned as a 2-D 
%array, 'sy'. 
%
%The input variables are
%an      : L-level DWT of a 2-D array
%lpf, hpf: these two filters define the synthesis filter bank
%OR
%fopt    :Takes the values of 1 and 2 and correspond to the 7/9 and 
%         9/7 filter banks used by FBI for their fingerprint compression
%         scheme. They correspond to options 1 and 2 in the analysis 
%         routine respectively.
%L       : Number of levels of decomposition and hence synthesis.
%
%The output 'sy' can be plotted using the commands 'image' or 'imagesc'
%and the command 'colormap(gray)' to specify the color map. Please refer
%to online help for more information.
%
%The final result of the synthesis procedure is plotted at the end 
%of the routine anyway.
%
%Refer to Chapter 4 for information on biorthogonal wavelet 
%decomposition and reconstruction and 2-D separable wavelet transform. 
%
%Author: Ajit S. Bopardikar
%Copyright (c) 1998 by Addison Wesley Longman, Inc.
%

num = nargin; %number of input arguments

  if (num ==3)
    levs = sh;
   if(sl == 1)
     sl =[-0.06453888262894 -0.04068941760956 0.41809227322221 0.78848561640566 0.41809227322221 -0.04068941760956 -0.06453888262894];
     sh =[0.03782845550700 0.02384946501938 -0.11062440441840 -0.37740285561265 0.85269867900940 -0.37740285561265 -0.11062440441840 0.02384946501938 0.03782845550700];
   elseif (sl >=2)
      if (sl > 2)
      fprintf('fopt chosen to be greater than 2. Using fopt=2 instead\n');
      end; 
     sl =[0.03782845550700 -0.02384946501938 -0.11062440441842 0.37740285561265 0.85269867900940 0.37740285561265 -0.11062440441842 -0.02384946501938 0.03782845550700];
     sh =[0.06453888262894 -0.04068941760956 -0.41809227322221 0.78848561640566 -0.41809227322221 -0.04068941760956 0.06453888262894];
   end %end inner if
  end %end if

  [m,n] = size(an);

%Determine the dimension of each low-low subband
   ms = [m]; %initialize the arrays
   ns = [n]; %initialize the arrays 
   
   %for rows
   for i=1:(levs-1)
      if (m/2 == round(m/2)) %even number of rows
        m = m/2;
      else %odd number of rows
        if (length(sl) > length(sh)) 
          m = floor(m/2);
        else
          m = ceil(m/2);
        end %end inner if
      end %end if - this finishes the rows

      if(n/2 == round(n/2)) %even number of columns
        n = n/2;
      else
        if (length(sl) > length(sh))
          n = floor(n/2);
        else
          n = ceil(n/2);
        end %end inner if
      end %end if - this finishes the columns

        ms = [m ms];
        ns = [n ns];
   end %end for

%here we begin the synthesis process
   for i=1:levs
     sy = an(1:ms(i),1:ns(i)); %choose the appropriate part 

     sy = wsss1(sy,sl,sh); %one level of synthesis

     an(1:ms(i),1:ns(i)) = sy; %put back the reconstruction
   end %endfor
  
%plot the reconsructed array
    figure;colormap(gray);imagesc(sy);title('IDWT of the Input DWT Array')