Two-dimensional filtering.



  Y = FILTER2(B,X) filters the data in X with the 2-D FIR

  filter in the matrix B.  The result, Y, is computed 

  using 2-D convolution and is the same size as X.



  Y = FILTER2(B,X,'shape') returns Y computed via 2-D

  convolution with size specified by 'shape':

    'same'  - (default) returns the central part of the 

              convolution that is the same size as X.

    'valid' - returns only those parts of the convolution

              that are computed without the zero-padded

              edges, size(Y) < size(X).

    'full'  - returns the full 2-D convolution, 

              size(Y) > size(X).



  See also CONV26SJI0ZJ.