function [I_W , S] = func_DWT(I, level, Lo_D, Hi_D)
% Matlab implementation of SPIHT (without Arithmatic coding stage)
%
% Wavelet decomposition
%
% input: I : input image
% level : wavelet decomposition level
% Lo_D : low-pass decomposition filter
% Hi_D : high-pass decomposition filter
%
% output: I_W : decomposed image vector
% S : corresponding bookkeeping matrix
%
% please refer wavedec2 function to see more
%
% Jing Tian
% Contact me : scuteejtian@hotmail.com
% This program is part of my undergraduate project in GuangZhou, P. R. China.
% April - July 1999
[C,S] = func_Mywavedec2(I,level,Lo_D,Hi_D);
S(:,3) = S(:,1).*S(:,2); % dim of detail coef nmatrices
L = length(S);
I_W = zeros(S(L,1),S(L,2));
% approx part
I_W( 1:S(1,1) , 1:S(1,2) ) = reshape(C(1:S(1,3)),S(1,1:2));
for k = 2 : L-1
rows = sum(S(1:k-1,1))+1:sum(S(1:k,1));
columns = sum(S(1:k-1,2))+1:sum(S(1:k,2));
% horizontal part
c_start = S(1,3) + 3*sum(S(2:k-1,3)) + 1;
c_stop = S(1,3) + 3*sum(S(2:k-1,3)) + S(k,3);
I_W( 1:S(k,1) , columns ) = reshape( C(c_start:c_stop) , S(k,1:2) );
% vertical part
c_start = S(1,3) + 3*sum(S(2:k-1,3)) + S(k,3) + 1;
c_stop = S(1,3) + 3*sum(S(2:k-1,3)) + 2*S(k,3);
I_W( rows , 1:S(k,2) ) = reshape( C(c_start:c_stop) , S(k,1:2) );
% diagonal part
c_start = S(1,3) + 3*sum(S(2:k-1,3)) + 2*S(k,3) + 1;
c_stop = S(1,3) + 3*sum(S(2:k,3));
I_W( rows , columns ) = reshape( C(c_start:c_stop) , S(k,1:2) );
end
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