% -*- texinfo -*-
% @deftypefn {Function File} {@var{y} =} filter2 (@var{b}, @var{x})
% @deftypefnx {Function File} {@var{y} =} filter2 (@var{b}, @var{x}, @var{shape})
% Apply the 2-D FIR filter @var{b} to @var{x}. If the argument
% @var{shape} is specified, return an array of the desired shape.
% Possible values are:
%
% @table @asis
% @item 'full'
% pad @var{x} with zeros on all sides before filtering.
% @item 'same'
% unpadded @var{x} (default)
% @item 'valid'
% trim @var{x} after filtering so edge effects are no included.
% @end table
%
% Note this is just a variation on convolution, with the parameters
% reversed and @var{b} rotated 180 degrees.
% @seealso{conv2}
% @end deftypefn