## Copyright (C) 2000 Kai Habel <kai.habel@gmx.de>
## Copyright (C) 2011, 2015 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/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} isind (@var{img})
## Return true if @var{img} is an indexed image.
##
## A variable can be considered an indexed image if it is a non-sparse,
## real array of size @nospell{MxNx1xK}, and:
##
## @itemize @bullet
## @item of class double with all integers above zero;
## @item of class uint8 or uint16.
## @end itemize
##
## @emph{Note}: despite their suggestive names, the functions isbw,
## isgray, isind, and isrgb, are ambiguous since it is not always possible
## to distinguish between those image types.  For example: an uint8 matrix
## can be both a grayscale and indexed image; a grayscale image may have
## values outside the range [0 1].  They are good to dismiss input as an
## invalid image type, but not for identification.
##
## @seealso{ind2gray, ind2rgb, isbw, isgray, isindex, isrgb}
## @end deftypefn

function bool = isind (img)

  if (nargin != 1)
    print_usage;
  endif

  bool = false;
  if (isimage (img) && ndims (img) < 5 && size (img, 3) == 1)
    if (isfloat (img))
      bool = isindex (img);
    elseif (any (isa (img, {"uint8", "uint16"})))
      bool = true;
    endif
  endif

endfunction

%!assert (isind ([]), false);
%!assert (isind (1:10), true);
%!assert (isind (0:10), false);
%!assert (isind (1), true);
%!assert (isind (0), false);
%!assert (isind ([1.3 2.4]), false);
%!assert (isind ([1 2; 3 4]), true);
%!assert (isind (randi (100, 10, 10, 1, 4)), true);
%!assert (isind (randi (100, 10, 10, 3, 4)), false);
%!assert (isind (randi (100, 10, 10, 1, 4, 2)), false);
