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## -*- texinfo -*-
## @deftypefn  {} {@var{map} =} hsv ()
## @deftypefnx {} {@var{map} =} hsv (@var{n})
## Create color colormap.  This colormap begins with red, changes through
## yellow, green, cyan, blue, and magenta, before returning to red.
##
## It is useful for displaying periodic functions.  The map is obtained by
## linearly varying the hue through all possible values while keeping constant
## maximum saturation and value.  The equivalent code is
## @code{hsv2rgb ([(0:N-1)'/N, ones(N,2)])}.
##
## 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 = hsv (n)

  if (nargin == 1)
    if (! (isscalar (n) && isreal (n) && n == fix (n)))
      error ("hsv: 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 = [1, 0, 0];
  elseif (n > 1)
    hue = [0:n-1]' / n;
    map = hsv2rgb ([hue, ones(n,1), ones(n,1)]);
  else
    map = zeros (0, 3);
  endif

endfunction


## A better demo of this colormap would be to plot the hsv values.
%!demo
%! ## Show the 'hsv' colormap profile and as an image
%! cmap = hsv (256);
%! subplot (2, 1, 1);
%!  rgbplot (cmap, "composite");
%! subplot (2, 1, 2);
%!  rgbplot (cmap);

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

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

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

%!assert (hsv (6)(:), [1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1]')

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