wiener2.m

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function [f,noise] = wiener2(varargin)
%WIENER2 Perform 2-D adaptive noise-removal filtering.
%   WIENER2 lowpass filters an intensity image that has been
%   degraded by constant power additive noise. WIENER2 uses a
%   pixel-wise adaptive Wiener method based on statistics
%   estimated from a local neighborhood of each pixel.
%
%   J = WIENER2(I,[M N],NOISE) filters the image I using
%   pixel-wise adaptive Wiener filtering, using neighborhoods of
%   size M-by-N to estimate the local image mean and standard
%   deviation. If you omit the [M N] argument, M and N default to
%   3. The additive noise (Gaussian white noise) power is assumed
%   to be NOISE.
%
%   [J,NOISE] = WIENER2(I,[M N]) also estimates the additive
%   noise power before doing the filtering. WIENER2 returns this
%   estimate as NOISE.
%
%   Class Support
%   -------------
%   The input image I can be of class uint8 or double. The output
%   image J is of the same class as I.
%
%   Example
%   -------
%       I = imread('saturn.tif');
%       J = imnoise(I,'gaussian',0,0.005);
%       K = wiener2(J,[5 5]);
%       imshow(J), figure, imshow(K)
%
%   See also FILTER2, MEDFILT2.

%   The following syntax is grandfathered:
%
%   J = WIENER2(I,[M N],[MBLOCK NBLOCK],NOISE) or [J,NOISE] =
%   WIENER2(I,[M N],[MBLOCK NBLOCK]) processes the intensity
%   image I as above but in blocks of size MBLOCK-by-NBLOCK.  Use
%   J = WIENER2(I,[M N],SIZE(I),NOISE) to process the matrix all
%   at once. 

%   Clay M. Thompson 2-17-93
%   Revised Steven L. Eddins, November 1996
%   Copyright 1993-1998 The MathWorks, Inc.  All Rights Reserved.
%   $Revision: 5.9 $  $Date: 1997/11/24 15:36:36 $

% Uses algorithm developed by Lee (1980).
% Reference: "Two-Dimensional Signal and Image Processing" by 
% Jae S. Lim, pp.536-540.

[g, nhood, block, noise, msg] = ParseInputs(varargin{:});
if (~isempty(msg))
  error(msg);
end

if isa(g, 'uint8')
  u8out = 1;
  if (islogical(g))
    % It doesn't make much sense to pass a binary image
    % in to this function, but just in case.
    logicalOut = 1;
    g = double(g);
  else
    logicalOut = 0;  
    g = double(g)/255;    
  end
else
  u8out = 0;
end

% Estimate the local mean of f.
localMean = filter2(ones(nhood), g) / prod(nhood);

% Estimate of the local variance of f.
localVar = filter2(ones(nhood), g.^2) / prod(nhood) - localMean.^2;

% Estimate the noise power if necessary.
if (isempty(noise))
  noise = mean2(localVar);
end

% Compute result
% f = localMean + (max(0, localVar - noise) ./ ...
%           max(localVar, noise)) .* (g - localMean);
%
% Computation is split up to minimize use of memory
% for temp arrays.
f = g - localMean;
g = localVar - noise; 
g = max(g, 0);
localVar = max(localVar, noise);
f = f ./ localVar;
f = f .* g;
f = f + localMean;

if u8out==1,
  if (logicalOut)
    f = uint8(f);
  else
    f = uint8(round(f*255));
  end
end


%%%
%%% Subfunction ParseInputs
%%%
function [g, nhood, block, noise, msg] = ParseInputs(varargin)

g = [];
nhood = [3 3];
block = [];
noise = [];
msg = '';

switch nargin
case 0
    msg = 'Too few input arguments';
    return;
    
case 1
    % wiener2(I)
    
    g = varargin{1};
    
case 2
    g = varargin{1};
    switch prod(size(varargin{2}))
    case 1
        % wiener2(I,noise)
        
        noise = varargin{2};
        
    case 2
        % wiener2(I,[m n])

        nhood = varargin{2};
        
    otherwise
        msg = 'Invalid input syntax';
        return;
    end
    
case 3
    g = varargin{1};
    if (prod(size(varargin{3})) == 2)
        % wiener2(I,[m n],[mblock nblock])  GRANDFATHERED
        nhood = varargin{2};
        block = varargin{3};
        
    else
        % wiener2(I,[m n],noise)
        nhood = varargin{2};
        noise = varargin{3};
    end
    
case 4
    % wiener2(I,[m n],[mblock nblock],noise)  GRANDFATHERED
    g = varargin{1};
    nhood = varargin{2};
    block = varargin{3};
    noise = varargin{4};
    
otherwise
    msg = 'Too many input arguments';
    return;
end

if (isempty(block))
    block = bestblk(size(g));
end