function demohaar2;
%
% 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=4;
N=2^n;
for k=0:n-1
    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=zeros(N,N)
        A(i+1:2^k:i+2^k+1,j+1:2^k:j+2^k+1)=10*4^k*ones(2,2)
        pause(0.2*2^k)
    end
    end
end
end