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function fft_img = get_FFT() % **************************************** ****************************************************************************************************************************
% Compute the FFT phase or Amplitude
 
Amplitude

CtrlFigHdl              = GetFigHdl('CtrlFig');
ToggleButtonAmpHdl      = findobj(CtrlFigHdl, 'Tag', 'ToggleButtonAmp');
ToggleButtonPhaseHdl    = findobj(CtrlFigHdl, 'Tag', 'ToggleButtonPhase');
 
'ToggleButtonPhase');

% detect if we want a Phase or Amplitude
if get(ToggleButtonAmpHdl, 'Value')
    BufferType = 1;  % FFT Amplitude type
elseif get(ToggleButtonPhaseHdl, 'Value')
    BufferType = 2;  % FFT Phase type
else
    fft_img = [];
    return;
end
 
end

CtrlFigUsrDat = get(CtrlFigHdl, 'UserData');
 
'UserData');

% Do we need to update the FFT?
if (BufferType == CtrlFigUsrDat.Current.BufferType) && ~isempty(CtrlFigUsrDat.Current.Buffer)
    % No we don't
    fft_img = CtrlFigUsrDat.Current.Buffer;
else
    % we need to compute a new fft
    % Notes: fft(uint16) is double; fft(single) is single; fft(double) is double
 
double

    clear CtrlFigUsrDat; % Avoid duplication of data
 CtrlFigUsrDat = ClearBuffer('main'); % makes room

 % Get the ROI limits
 [ROI_min_x ROI_max_x ROI_min_y ROI_max_y] = getROIlimits();

 try
     h = [];

     % pre-allocation. We make it single as it's half the data needed and still good enough. 
     % The FFT computation below is converted in single as it is done, plane by plane
     fft_img = zeros(ROI_max_y-ROI_min_y+1, ROI_max_x-ROI_min_x+1, CtrlFigUsrDat.Current.z_dim, 'single');

     sizeOfSingle = 4;

     h = waitbar(0,[num2str(size(fft_img,2)) ' * ' num2str(size(fft_img,1)) ' pixels * ', ...
         num2str(size(fft_img,3)) ' frames * single (32 bpp) = ' num2str(numel(fft_img)*sizeOfSingle/(1024*1024),'%.2f'), ' MB'], ...
         'Name', 'Computing FFT...', 'WindowStyle', 'modal');
     set(h, 'HandleVisibility', 'off'); % do not integrate this into the line above
     pause(0.1); % allow refresh

     if BufferType == 1 % Amplitude
         for i = ROI_min_x:ROI_max_x % along x
             fft_img( : , i-ROI_min_x+1 , :) = abs(fft(single(get_RawData('ROI',i,':')),[],3));
              if ishandle(h)
                  waitbar((i-ROI_min_x+1)/(ROI_max_x-ROI_min_x+1), h);
              else
                  error('FFT aborted.');
              end                
         end
     else % Phase
         for i = ROI_min_x:ROI_max_x % along x
             fft_img( : , i-ROI_min_x+1 , :) = -angle(fft(single(get_RawData('ROI',i,':')),[],3));
              if ishandle(h)
                  waitbar((i-ROI_min_x+1)/(ROI_max_x-ROI_min_x+1), h);
              else
                  error('FFT aborted.');
              end
         end
     end

     % Update Buffer
     CtrlFigUsrDat.Current.BufferType = BufferType;
     CtrlFigUsrDat.Current.Buffer     = fft_img;
     setF(CtrlFigHdl, 'UserData', CtrlFigUsrDat);
 catch FFTError
     messageBox(FFTError.message, 1, 'FFT Error');
     fft_img = []; % means it failed computing the FFT
 end    

 if ishandle(h)
     delete(h)
    end

end
  
end