%IM_FFT Fixed mapping for 2D FFT
%
% F = IM_FFT(A,POST1,POST2,...)
% F = A*IM_FFT([],POST1,POST2,...)
% F = A*IM_FFT(POST1,POST2,...)
%
% INPUT
% A Dataset with object images (possibly multi-band)
%
% OUTPUT
% F Dataset with FFT images
% POST1 Characterstring defining postprocessing by FILTIM
% POST2 Characterstring defining more postprocessing by FILTIM
%
% DESCRIPTION
% This routine applies the 2D FFT2 routine to all images in A. The result
% is complex. See the below example for post processing by FILTIM. It shows
% how it can be integrated in the call to IM_FFT.
%
% EXAMPLE
% delfigs
% prdatafiles; % make sure PRDATAFILES is in the path
% a = delft_idb; % load the Delft Image DataBase
% x = a*gendat(4); % load a subset of 4 images
% % show the centralized log of the powerspectra of the gray images
% show(x*im_gray*im_fft*filtim('abs')*filtim('fftshift')*filtim('log'));
% % post-processing can be included in im_fft
% figure; show(x*im_gray*im_fft('abs','fftshift','log'));
% figure; show(x); % show the originals
% showfigs
%
% SEE ALSO (<a href="http://37steps.com/prtools">PRTools Guide</a>)
% DATASETS, DATAFILES, FFT2, FILTIM
% Copyright: R.P.W. Duin, r.p.w.duin@37steps.com
function b = im_fft(varargin)
if nargin==0, varargin = {[]}; end
varargin = shiftargin(varargin,'char');
a = varargin{1};
if isempty(a)
b = prmapping(mfilename,'fixed',varargin(2:end));
b = setname(b,'Image FFT');
elseif isa(a,'prdataset') % allows datafiles too
isobjim(a);
b = filtim(a,mfilename,varargin(2:end));
b = setfeatsize(b,getfeatsize(a));
elseif isa(a,'double') || isa(a,'dip_image') % here we have a single image
a = double(a);
b = fft2(a);
if numel(varargin) > 1
for j=2:numel(varargin)
b = filtim(b,varargin{j});
end
end
end
return