Code covered by the BSD License

# Bias Field Corrected Fuzzy C-Means

### Dirk-Jan Kroon (view profile)

02 Nov 2009 (Updated )

Estimates the illumination artifact in 2D (color) and 3D CT and MRI and segments into classes.

I=imgaussian(I,sigma,siz)
```function I=imgaussian(I,sigma,siz)
% IMGAUSSIAN filters an 1D, 2D color/greyscale or 3D image with an
% gaussian filter. This function uses for filtering IMFILTER or if
% compiled the fast  mex code imgaussian.c . Instead of using a
% multidimensional gaussian kernel, it uses the fact that a gaussian
% filter can be separated in 1D gaussian kernels.
%
% J=IMGAUSSIAN(I,SIGMA,SIZE)
%
% inputs,
%   I: The 1D, 2D greyscale/color, or 3D input image
%   SIGMA: The sigma used for the gaussian
%   SIZE: Kernel size (single value) (default: sigma*6)
%
% outputs,
%   J: The gaussian filterd image
%
% note, compile the code with: mex imgaussian.c -v
%
% example,
%   I = im2double(imread('peppers.png'));
%   figure, imshow(imgaussian(I,3));
%
% Function is written by D.Kroon University of Twente (September 2009)

if(~exist('siz','var')), siz=sigma*6; end

if(sigma>0)
% Make 1D gaussian kernel
x=-ceil(siz/2):ceil(siz/2);
H = exp(-(x.^2/(2*sigma^2)));
H = H/sum(H(:));

% Filter each dimension with the 1D gaussian kernels\
if(ndims(I)==1)
I=imfilter(I,H, 'same' ,'replicate');
elseif(ndims(I)==2)
Hx=reshape(H,[length(H) 1]);
Hy=reshape(H,[1 length(H)]);
I=imfilter(imfilter(I,Hx, 'same' ,'replicate'),Hy, 'same' ,'replicate');
elseif(ndims(I)==3)
if(size(I,3)<4) % Detect if 3D or color image
Hx=reshape(H,[length(H) 1]);
Hy=reshape(H,[1 length(H)]);
for k=1:size(I,3)
I(:,:,k)=imfilter(imfilter(I(:,:,k),Hx, 'same' ,'replicate'),Hy, 'same' ,'replicate');
end
else
Hx=reshape(H,[length(H) 1 1]);
Hy=reshape(H,[1 length(H) 1]);
Hz=reshape(H,[1 1 length(H)]);
I=imfilter(imfilter(imfilter(I,Hx, 'same' ,'replicate'),Hy, 'same' ,'replicate'),Hz, 'same' ,'replicate');
end
else
error('imgaussian:input','unsupported input dimension');
end
end```