synthh2d.m

这是伯克里wavelet transforms一书中的例子的代码

function sy = synthh2d(an,sl,sh,levs);
%Routine to reconstruct the multilevel DWT decomposed 2-D signal using 
%even length or half sample symmetric (HSS) separable biorthogonal 
%filter bank. Symmetric extension used to extend the subbands for 
%synthesis. This corresponds to the analysis routine 'analh2d'.
%
%sy = synthh2d(an,lpf,hpf,L) reconstructs a 2-D array, from its DWT, an,
%which could be the output of the routine 'analh2d'.
%The image is assumed to be decomposed to L levels. The WSS filter 
%bank used is comprised of sl and sh. If this corresponds to the 
%analysis filter bank used for DWT, then you get perfect 
%reconstruction. The reconstructed image is returned in 'sy'.
%
%sy = synthh2d(an,fopt,L) reconstructs a 2-D array, from its DWT an,
%which could be the output of the routine 'analh2d'.
%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 in '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, 2 or 3 and correspond to the 6/2, 2/6 and 
%         4/4 tap HSS filter banks respectively.
%L       : Number of levels of decomposition and hence synthesis.
%
%The reconstructed image returned in 'sy' can be plotted using the 
%'image' or the 'imagesc' commands in conjunction with the 'colormap'
%command to specify the color map. Please refer to the online help
%for more information.
%
%The reconstructed image 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 =[-0.17677669529664 0.17677669529664 0.70710678118655 0.70710678118655 0.17677669529664  -0.17677669529664];
     sh =[-0.70710678118655   0.70710678118655];
   elseif (sl ==2)
     sl =[0.70710678118655   0.70710678118655];
     sh =[-0.17677669529664 -0.17677669529664 0.70710678118655 -0.70710678118655 0.17677669529664 0.17677669529664];
   elseif (sl >=3)
      if (sl > 3)
      fprintf('fopt chosen to be greater than 3. Using fopt= 3 instead\n');
      end; 
     sl =[-0.35355339059327 1.06066017177982 1.06066017177982 -0.35355339059327];
     sh =[-0.17677669529664 0.53033008588991 -0.53033008588991 0.17677669529664];
   end %end inner if
  end %enf if
  
  [m,n] = size(an);

  ms = [m]; %initialize
  ns = [n]; %initialize
  
  %compute the subband sizes
  for i = 1:levs-1
    if (length(sh)/4 == round(length(sh)/4)) 
      if(m/2 == round(m/2))
        m = m/2;
      else
        m = (m+1)/2;
      end %end inner if
    else
      if (m/2 == round(m/2))
        m = m/2 +1 ;
      else
        m = (m+1)/2;
      end %end inner if
    end % end if

    if (length(sh)/4 == round(length(sh)/4)) 
      if(n/2 == round(n/2))
        n = n/2;
      else
        n = (n+1)/2;
      end %end inner if
    else
      if (n/2 == round(n/2))
        n = n/2 +1 ;
      else
        n = (n+1)/2;
      end %end inner if
    end % end if

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

  for i = 1:levs
    sy = an(1:ms(i),1:ns(i)); %isolate the highest level
     
    sy = hsss1(sy,sl,sh); %one level synthesis
    an(1:ms(i),1:ns(i)) = sy;
  end %endfor
  
  %plot the reconstructed array
  figure;colormap(gray);imagesc(sy);title('IDWT of Input DWT Array');