function A=invfasthaar2(A);
%
% first attempt of a FAST 2dim Haar wavelet transform
% ovrwriting the original matrix
% working from the finest level up, replace each
% 2x2 block by average in top left, and differences
% along horizontal, vertical, diagonal in other 3
% this is implemented by reshape and matrixmult
% then recursively consider only top left entries
% of each block, and do THE SAME operation to each
%
% eventually want to code the inverse similarily
% and to display basis elements and lin comb's
% as rastered images
% quality measure is energy in each frequency
% and in vertical / horizontal variation and
% diagonal dominance
%
% first attempt August 2008
N=size(A,1);
n=log(N)/log(2);
image(32*(A+1))
pause
T=[1 1 1 1;1 1 -1 -1;1 -1 1 -1;1 -1 -1 1]/2;
for k=n-1:-1:0
    for i=0:2^(k+1):N-2
    for j=0:2^(k+1):N-2
        M=[i+1:i+2,j+1:j+2];
        A(i+1:2^k:i+2^k+1,j+1:2^k:j+2^k+1)=...
            reshape(T'*reshape(A(i+1:2^k:i+2^k+1,j+1:2^k:j+2^k+1),4,1),2,2);
        image(32*(A+1))
        pause
    end
    end
    pause
end
A
pause
end