function psfPrecMatData = zeroPrecMatrix( PSFs, center, b, tol )%%       psfPrecMatData = zeroPrecMatrix( PSFs, center, b, tol );%%  Construct psfPrec matrix data using zero boundary condtions.%%  Given (several) PSFs, the locations of the corresponding point sources, %  and the boudary condition, this function sets up the data (eigenvalues)%  needed for a circulant preconditioner defined by the PSFs.%%  Input:%        PSFs  -  cell array containing the PSFs%      center  -  cell array with {i,j,k} entry containing%                 [row_index, col_index, k_index] of point source location for%                 PSF{i,j,k}%           b  -  blurred image%%  Optional Input:%         tol  -  cell array containing the tolerance used to "regularize" the %                 preconditioner for each individual PSF%                 (e.g., using Hanke, Nagy, Plemmons approach) %%  Output:%   psfPrecMatData -  cell array containing the data needed for the%                     preconditioner solve routines%%  J. Nagy  &  K. Lee 2/8/02if nargin < 4  tol = [];endimsize=size(b);if length(imsize)==1  imsize = [imsize,1,1];elseif length(imsize) == 2  imsize = [imsize,1];endnregions=size(PSFs);if length(nregions)==1  nregions = [nregions,1,1];elseif length(nregions) == 2  nregions = [nregions,1];endrsize = ceil(imsize ./ nregions);%%  In order for this to be consistent for 2-D and 3-D images, we need to make%  sure there is a third dimension ...%if length(imsize) == 1  imsize = [imsize, 1, 1];  rsize = [rsize, 1, 1];  nregions = [nregions, 1, 1];elseif length(imsize) == 2  imsize = [imsize, 1];  rsize = [rsize, 1];  nregions = [nregions, 1];end%%  Coding the rest of this will be easier if all of the image subregions%  have the same dimensions.  If it's not, we pad with a few zeros to make%  it so ...%padsize1 = rsize .* nregions - imsize;if any( padsize1 < 0 )  error('Something is wrong here ...')endb = padarray(b, padsize1, 'post');%%  Now we get information about beginning and ending indices of subregions%  so we can "get" subregions correctly ...%[RIidx, RJidx, RKidx] = region_indices( nregions, rsize );psfPrecMatData = cell(nregions);if isempty(tol)  for k = 1:size(PSFs,3)    for i = 1:size(PSFs,1)      for j = 1:size(PSFs,2)        PSF = PSFs{i,j,k};        c = center{i,j,k};        bsub = b(RIidx(i,1):RIidx(i,2), RJidx(j,1):RJidx(j,2), RKidx(k,1):RKidx(k,2));        psfPrecMatData{i,j,k} = zeroPrecMatrixOnePsf(PSF, c, bsub);      end    end  endelseif isnumeric(tol)                            % if a single value for tol is given,    % tol = num2cell( tol * ones(size(PSFs)) );  % use it for all PSFs    for k = 1:size(PSFs,3)    for i = 1:size(PSFs,1)      for j = 1:size(PSFs,2)        PSF = PSFs{i,j,k};        c = center{i,j,k};        %t = tol{i,j,k};        bsub = b(RIidx(i,1):RIidx(i,2), RJidx(j,1):RJidx(j,2), RKidx(k,1):RKidx(k,2));        psfPrecMatData{i,j,k} = zeroPrecMatrixOnePsf(PSF, c, bsub, tol);      end    end  endelse  if ischar(tol)                         % if 'help' is given for tol,     tol = 'help';                        % use it for all PSFs  end  for k = 1:size(PSFs,3)    for i = 1:size(PSFs,1)      for j = 1:size(PSFs,2)        PSF = PSFs{i,j,k};        c = center{i,j,k};        t = 'help';        bsub = b(RIidx(i,1):RIidx(i,2), RJidx(j,1):RJidx(j,2), RKidx(k,1):RKidx(k,2));        psfPrecMatData{i,j,k} = zeroPrecMatrixOnePsf(PSF, c, bsub, 'help');      end    end  endend