SubbandThresholding(subb)

function t_subb = SubbandThresholding(subb)
% Threshold the noisy subband according to BlockShrink rule
%
% subb: inputted noisy subband
% t_subb: outputted thresholded subband
%
% Author: Zhou Dengwen
% [e-mail]
% Department of Computer Science & Technology
% North China Electric Power University(Beijing)(NCEPU)
%
% Reference(s):
% Zhou Dengwen and Shen Xiaoliu, "Image denoising using block
% thresholding," in Proc. 2008 congress on image and signal 
% processing,Sanya, Hainan, ChinaMay 2008, pp. 335C338.
%
% Last time modified: Jun. 10, 2009
%

% Read the size of the coef. matrix
[nRow,nCol] = size(subb);

% Estimate the block size and threshold of the subband
[LB,thres] = Parameters(subb);
LB = round(LB);

% Threshold the coef. matrix
t_subb = zeros(nRow,nCol);
for i = 1:nRow/LB
    for j = 1:nCol/LB
        b1 = (i-1)*LB; b2 = (j-1)*LB;
        bm = subb(b1+1:b1+LB,b2+1:b2+LB);
        Sb = sum(bm(:).^2);
        factor = max(1-thres/Sb,0);
        t_subb(b1+1:b1+LB,b2+1:b2+LB) = factor*bm;
    end
end