normnoise.m

来自「denoising image with DWT」· M 代码 · 共 46 行

function [y,coef] = NormNoise(x,qmf)
% NormNoise -- Estimates noise level, Normalize signal to noise level 1
%  Usage
%    [y,coef] = NormNoise(x,qmf)
%  Inputs
%    x     1-d signal
%    qmf   quadrature mirror filter
%  Outputs
%    y     1-d signal, scaled so wavelet coefficients
%          at finest level have median absolute deviation 1.
%    coef  estimation of 1/sigma
%
%  Description
%    This is required pre-processing to use any of the DeNoising
%    tools on naturally-occurring data.
%
%  See Also
%    WaveShrink, CPDeNoise,WPDeNoise
%
	u = DownDyadHi(x,qmf);
	s = median(abs(u));
	if s ~= 0
		y =  .6745 .* x ./s;
                coef = .6745 /s;
	else
		y = x;
                coef = 1;
	end

%
% Copyright (c) 1993-5.  Jonathan Buckheit, David Donoho and Iain Johnstone
%
% Modified by Maureen Clerc and Jerome Kalifa, 1997
% [e-mail], [e-mail]
%
    
    
 
 
%
%  Part of Wavelab Version 850
%  Built Tue Jan  3 13:20:39 EST 2006
%  This is Copyrighted Material
%  For Copying permissions see COPYING.m
%  Comments? e-mail [e-mail]