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## distribution or <https://octave.org/copyright/>.
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## -*- texinfo -*-
## @deftypefn  {} {@var{map} =} gray ()
## @deftypefnx {} {@var{map} =} gray (@var{n})
## Create gray colormap.  This colormap varies from black to white with shades
## of gray.
##
## The argument @var{n} must be a scalar.
## If @var{n} is not specified the length of the current colormap is used.  If
## there is no current colormap the default value of 256 is used.
## @seealso{colormap}
## @end deftypefn

function map = gray (n)

  if (nargin == 1)
    if (! (isscalar (n) && isreal (n) && n == fix (n)))
      error ("gray: N must be a scalar integer");
    endif
    n = double (n);
  else
    hf = get (0, "currentfigure");
    if (! isempty (hf))
      n = rows (get (hf, "colormap"));
    else
      n = 256;
    endif
  endif

  if (n == 1)
    map = [0, 0, 0];
  elseif (n > 1)
    gr = [0:(n-1)]' / (n - 1);
    map = [gr, gr, gr];
  else
    map = zeros (0, 3);
  endif

endfunction


%!demo
%! ## Show the 'gray' colormap profile and as an image
%! cmap = gray (16);
%! subplot (2, 1, 1);
%!  rgbplot (cmap, "composite");
%! subplot (2, 1, 2);
%!  rgbplot (cmap);


%!assert (size (gray ()), [256, 3])
%!assert (size (gray (16)), [16, 3])

%!assert (gray (1), [0, 0, 0])
%!assert (gray (true), double ([0, 0, 0]))
%!assert (gray (char (1)), double ([0, 0, 0]))
%!assert (gray (int32 (1)), double ([0, 0, 0]))

%!assert (gray (0), zeros (0, 3))
%!assert (gray (-1), zeros (0, 3))

%!assert (gray (11), [0:.1:1]' .* [1, 1, 1], eps)

## Input validation
%!error <N must be a scalar integer> gray ("foo")
%!error <N must be a scalar integer> gray ([1, 2, 3])
%!error <N must be a scalar integer> gray ({1, 2, 3})
