gistfile1.matlab

function smim = REDUCE(im)

    wgt = [0.0500    0.2500    0.4000    0.2500    0.0500];
    m = -2:2;
    
    smim = zeros(ceil(size(im,1)/2), ceil(size(im,2)/2));
    
    im = padarray(im, [2 2]);
    
    window = wgt'*wgt;
    
    for r=1:size(smim,1)
        for c=1:size(smim,2)
            A = im(2*r+m+1,2*c+m+1).*window;
            smim(r,c) = sum(A(:));
        end
    end
end

function lgim = EXPAND(im)

    wgt = [0.0500    0.2500    0.4000    0.2500    0.0500];
    m = -2:2;
    
    lgim = zeros(2*size(im,1), 2*size(im,2));
    
    im = padarray(im, [2 2]);
    
    window = wgt'*wgt;
    
    for r = 1:size(lgim,1)
        for c = 1:size(lgim,2)
            pxr = (r - m)/2 + 2;
            indr = find(floor(pxr)==pxr);
            
            pxc = (c - m)/2 + 2;
            indc = find(floor(pxc)==pxc);
            
            A = im(pxr(indr),pxc(indc)) .* window(m(indr)+3,m(indc)+3);
            lgim(r, c)= 4 * sum(A(:));
        end
    end
end