time   calls  line
                  1 function y = filter2(b,x,shape)
                  2 %FILTER2 Two-dimensional digital filter.
                  3 %   Y = FILTER2(B,X) filters the data in X with the 2-D FIR
                  4 %   filter in the matrix B.  The result, Y, is computed 
                  5 %   using 2-D correlation and is the same size as X. 
                  6 %
                  7 %   Y = FILTER2(B,X,'shape') returns Y computed via 2-D
                  8 %   correlation with size specified by 'shape':
                  9 %     'same'  - (default) returns the central part of the 
                 10 %               correlation that is the same size as X.
                 11 %     'valid' - returns only those parts of the correlation
                 12 %               that are computed without the zero-padded
                 13 %               edges, size(Y) < size(X).
                 14 %     'full'  - returns the full 2-D correlation, 
                 15 %               size(Y) > size(X).
                 16 %
                 17 %   FILTER2 uses CONV2 to do most of the work.  2-D correlation
                 18 %   is related to 2-D convolution by a 180 degree rotation of the
                 19 %   filter matrix.
                 20 %
                 21 %   Class support for inputs B,X:
                 22 %      float: double, single
                 23 %
                 24 %   See also FILTER, CONV2.
                 25 
                 26 %   Copyright 1984-2006 The MathWorks, Inc. 
                 27 %   $Revision: 5.13.4.5 $  $Date: 2010/09/02 13:35:21 $
                 28 
             2   29 error(nargchk(2,3,nargin,'struct')); 
             2   30 if nargin<3, shape = 'same'; end 
                 31 
             2   32 if (~isa(b,'float')),  b = double(b); end 
  0.01       2   33 if (~isa(x,'float')),  x = double(x); end 
                 34 
             2   35 code = [shape,' ']; code = code(1); 
             2   36 if isempty(find(code=='svf', 1)) 
                 37   error(message('MATLAB:filter2:InvalidParam'));
                 38 end
                 39 
             2   40 [mx,nx] = size(x); 
  0.01       2   41 stencil = rot90(b,2); 
             2   42 [ms,ns] = size(stencil); 
                 43 
                 44 % 1-D stencil?
             2   45 if (ms == 1) 
                 46   y = conv2(1,stencil,x,shape);
             2   47 elseif (ns == 1) 
                 48   y = conv2(stencil,1,x,shape);
             2   49 else 
             2   50   if (ms*ns > mx*nx) 
                 51     % The filter is bigger than the input.  This is a nontypical
                 52     % case, and it may be counterproductive to check the
                 53     % separability of the stencil.
             1   54     y = conv2(x,stencil,shape); 
             1   55   else 
             1   56     separable = false; 
             1   57     if all(isfinite(stencil(:))) 
                 58       % Check rank (separability) of stencil
             1   59       [u,s,v] = svd(stencil); 
             1   60       s = diag(s); 
             1   61       tol = length(stencil) * eps(max(s)); 
             1   62       rank = sum(s > tol);    
             1   63       separable = (rank ==1); 
             1   64     end 
             1   65     if separable 
                 66       % Separable stencil
             1   67       hcol = u(:,1) * sqrt(s(1)); 
             1   68       hrow = conj(v(:,1)) * sqrt(s(1)); 
             1   69       if (all(all((round(stencil) == stencil))) && all(all((round(x) == x)))) 
                 70         % Output should be integer
             1   71         y = round(conv2(hcol, hrow, x, shape)); 
                 72       else
                 73         y = conv2(hcol, hrow, x, shape);
                 74       end
                 75     else
                 76       % Nonseparable stencil
                 77       y = conv2(x,stencil,shape);
                 78     end
             1   79   end 
             2   80 end