ctCodes/makeDsMatrix.m at master · ndwork/ctCodes · GitHub

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function dsMatrix = makeDsMatrix( A, phi, x, y )

  Nx = numel(x);
  Ny = numel(y);
  nA = numel(A);
  nPhi = numel(phi);

  nNonzero = Ny * nA * nPhi;
  colIndxs = zeros( nNonzero, 1 );
  rowIndxs = zeros( nNonzero, 1 );
  values   = zeros( nNonzero, 1 );

  rowImg = (1:Ny)' * ones(1,Nx);
  colImg = ones(Ny,1) * (1:Nx);

  for i=1:nA*nPhi
    if mod(i,100)==0
      disp(['dsMatrix ', num2str(i), ' of ', num2str(nA*nPhi)]);
    end
    dsIn = zeros(nA,nPhi);
    dsIn(i) = 1;
    dsOut = dsTransform( dsIn, A, phi, x, y );

    nonzeroIndxs = find( dsOut ~= 0 );

    colIndxs( (i-1)*Ny + 1 : i*Ny ) = i;
    rowIndxs( (i-1)*Ny + 1 : i*Ny ) = nonzeroIndxs;
    values( (i-1)*Ny + 1 : i*Ny ) = dsOut( nonzeroIndxs );
  end

save( 'rowIndxs.mat', 'rowIndxs' );
save( 'colIndxs.mat', 'colIndxs' );
save( 'values.mat', 'values' );

  dsMatrix = sparse( rowIndxs, colIndxs, values, Ny*Nx, nA*nPhi );
end