function init_gaus_filt(filt_size)
global image_size data_base image_size_x image_size_y image_number
global threshold_level MatlabVersion
if isempty(MatlabVersion), MatlabVersion = version; end
if nargin < 1, filt_size = 1; end
spatial_filter = my_fspecial('gaussian',2*round(4*filt_size)+5,filt_size);
disp(['applying spatial gausian filter of size '...
 	num2str(filt_size)]);
for i=1:image_number
	mask = data_base(i,:)~=0;
	tmp = data_base(i,:); % +((1-mask)*mean(data_base(i,:)));
	tmp = reshape(tmp,image_size_x,image_size_y);
	tmp = filter2(spatial_filter,tmp);
	data_base(i,:) = reshape(tmp,1,image_size).*mask;
end
median_image = reshape(mean(data_base),image_size_x,image_size_y);