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## -*- texinfo -*-
## @deftypefn  {} {@var{map} =} pink ()
## @deftypefnx {} {@var{map} =} pink (@var{n})
## Create color colormap.  This colormap varies from black to white with
## shades of gray-pink.
##
## This colormap gives a sepia tone when used on grayscale images.
##
## 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 = pink (n)

  if (nargin == 1)
    if (! (isscalar (n) && isreal (n) && n == fix (n)))
      error ("pink: 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 = sqrt ([1/3, 1/3, 1/3]);
  elseif (n == 2)
    map = sqrt ([1/3, 1/3, 1/6
                  1    1    1 ]);
  elseif (n > 2)
    x = [0:(n-1)]' / (n-1);
    idx = floor (3/8 * n);
    base = 1 / (3 * idx);

    nel = idx;   # number of elements
    r(1:idx,1) = linspace (base, 2/3*x(idx) + 1/3, nel);
    r(idx+1:n,1) = 2/3*x(idx+1:n) + 1/3;

    g(1:idx,1) = 2/3*x(1:idx);
    g(idx:2*idx,1) = linspace (2/3*x(idx), 2/3*x(2*idx) + 1/3, nel+1);
    g(2*idx+1:n,1) = 2/3*x(2*idx+1:n) + 1/3;

    nel = n - 2*idx + 1;
    b(1:2*idx,1) = 2/3*x(1:2*idx);
    b(2*idx:n,1) = linspace (2/3*x(2*idx), 1, nel);

    map = sqrt ([r, g, b]);
  else
    map = zeros (0, 3);
  endif

endfunction


%!demo
%! ## Show the 'pink' colormap profile and as an image
%! cmap = pink (256);
%! subplot (2, 1, 1);
%!  rgbplot (cmap, "composite");
%! subplot (2, 1, 2);
%!  rgbplot (cmap);


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

%!assert (pink (1), sqrt ([1/3, 1/3, 1/3]), eps)
%!assert (pink (true), double (sqrt ([1/3, 1/3, 1/3])), eps)
%!assert (pink (char (1)), double (sqrt ([1/3, 1/3, 1/3])), eps)
%!assert (pink (int32 (1)), double (sqrt ([1/3, 1/3, 1/3])), eps)
%!assert (pink (2), sqrt ([1/3, 1/3, 1/6; 1, 1, 1]))

%!assert (pink (0), zeros (0, 3))
%!assert (pink (-1), zeros (0, 3))
%!assert (pink()(end,:), [1 1 1], eps)

%!test
%! a = sqrt ([1/3, 0,   0;
%!            5/9, 5/9, 2/9;
%!            7/9, 7/9, 11/18;
%!            1,   1,   1]);
%! assert (pink (4), a, eps)

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