www.pudn.com > SPIHT_bandelet.rar > perform_haar_transform_slow.m

function y = perform_haar_transform_slow(x, Jmin, dir); 
 
% perform_haar_transform - compute a wavelet haar transform 
% 
% y = perform_haar_transform(x, Jmin, dir); 
% 
%   This is the non-optimized Matlab version. 
%   TODO : code inverse transform (the mex version does implement it). 
% 
%   Copyright (c) 2004 Gabriel Peyré 
 
x = x(:); 
n = length(x); 
J = floor( log2(n) )-1; 
 
if nargin<3 
    dir=1; 
end 
 
if dir~=1 && dir~=-1 
	error('dir should be either +1 or -1.'); 
end 
 
if dir==-1 
    warning('Inverse haar transform not implemented');     
    y = x; 
    return; 
end 
 
 
% x contains the coarse scale signal 
y = x; 
for j=J:-1:0 
    n = length(x); 
    n1 = ceil(n/2); 
    n2 = floor(n/2); 
     
    % fine scale 
    y(n1+1:n) = ( x(1:2:2*n2) - x(2:2:2*n2) )/sqrt(2); 
    % coarse scale 
    if n1==n2 
        y(1:n1) = ( x(1:2:n) + x(2:2:n) )/sqrt(2); 
    else 
        y(1:n1-1) = ( x(1:2:n-1) + x(2:2:n) )/sqrt(2); 
        y(n1) = x(n); 
    end 
    x = y(1:n1); 
end 
 
return; 
 
 
% x contains the coarse scale signal 
y = x; 
for j=J:-1:0 
    n = length(x); 
    n1 = ceil(n/2); 
    n2 = floor(n/2); 
     
    if n1==n2 
        % coarse scale 
        y(1:n1) = ( x(1:2:n) + x(2:2:n) )/sqrt(2); 
        % fine scale 
        y(n1+1:n) = ( x(1:2:2*n2) - x(2:2:2*n2) )/sqrt(2); 
        x = y(1:n1); 
    else 
        % coarse scale 
        y(1:(n-3)/2) = ( x(1:2:n-3) + x(2:2:n-3) )/sqrt(2); 
        y((n-1)/2) = ( x(n-2) + x(n-1) + x(n) )/sqrt(3); 
        % fine scale 
        y(n1:n-1) = ( x(1:2:n-1) - x(2:2:n-1) )/sqrt(2); 
        y(n) = ( x(n-2) + x(n-1) - 2*x(n) )/sqrt(6); 
        x = y(1:n1-1); 
    end 
     
end 
 
return;