## Copyright (C) 2013 Carnë Draug <carandraug+dev@gmail.com>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, see <http://www.gnu.org/licenses/>.

## Private function to create a connectivity array
##
## Use the following Texinfo on the documentation of functions
## that make use of it (adjust the default)
##
## Element connectivity @var{conn}, to define the size of objects, can be
## specified with a numeric scalar (number of elements in the neighborhood):
##
## @table @samp
## @item 4 or 8
## for 2 dimensional matrices;
## @item 6, 18 or 26
## for 3 dimensional matrices;
## @end table
##
## or with a binary matrix representing a connectivity array.  Defaults to
## @code{conndef (ndims (@var{bw}), "maximal")} which is equivalent to
## @var{conn} of 8 and 26 for 2 and 3 dimensional matrices respectively.

function conn = make_conn (func, arg_pos, n_dims, conn)

  iptcheckconn (conn, func, "CONN", arg_pos);
  if (isscalar (conn))
    if (n_dims == 2)
      if (conn == 4)
        conn = [0 1 0
                1 1 1
                0 1 0];
      elseif (conn == 8)
        conn = [1 1 1
                1 1 1
                1 1 1];
      else
        error ("%s: CONN must have a value of 4 or 8 for 2 dimensional matrices",
               func);
      endif

    elseif (n_dims == 3)
      if (conn == 6)
        conn = false (3, 3, 3);
        conn(:,2,2) = true;
        conn(2,:,2) = true;
        conn(2,2,:) = true;
      elseif (conn == 18)
        conn = false (3, 3, 3);
        conn(2,:,:) = true;
        conn(:,2,:) = true;
        conn(:,:,2) = true;
      elseif (conn == 26)
        conn = true (3, 3, 3);
      else
        error (["%s: CONN must have a value of 6, 18, or 26 for 3 " ...
                "dimensional matrices"], func);
      endif
    else
      error (["%s: CONN must be defined as a binary matrix for matrices " ...
              "with more than 3 dimensions"], func);
    endif
  endif
endfunction