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########################################################################
##
## Copyright (C) 1999-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave 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.
##
## Octave 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 Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {@var{map} =} bone ()
## @deftypefnx {} {@var{map} =} bone (@var{n})
## Create color colormap. This colormap varies from black to white with
## gray-blue shades.
##
## The argument @var{n} must be a scalar.
## If unspecified, the length of the current colormap, or 64, is used.
## @seealso{colormap}
## @end deftypefn
function map = bone (n)
if (nargin == 1)
if (! isscalar (n))
error ("bone: N must be a scalar");
endif
n = double (n);
else
hf = get (0, "currentfigure");
if (! isempty (hf))
n = rows (get (hf, "colormap"));
else
n = 64;
endif
endif
if (n == 1)
map = [1/8 1/8 1/8];
elseif (n == 2)
map = [1/16 1/8 1/8
1 1 1 ];
elseif (n > 2)
x = [0:n-1]' / (n-1);
idx = floor (3/4*n);
nel = n - idx + 1; # number of elements
rem = mod (n, 8);
switch (rem)
case {2, 4}
base = 1 / (16 + 2*(n-rem));
case {5, 7}
base = 1 / (24 + 2*(n-rem));
otherwise
base = 0;
endswitch
r(1:idx,1) = 7/8 * x(1:idx);
r(idx:n,1) = linspace (7/8 * x(idx) + base, 1, nel);
idx = floor (3/8 * n);
nel = idx + 1;
g(1:idx,1) = 7/8 * x(1:idx);
g(idx:2*idx,1) = linspace (7/8 * x(idx), 7/8 * x(2*idx) + 1/8, nel);
g(2*idx+1:n,1) = 7/8 * x(2*idx+1:n) + 1/8;
base = 1 / (8*idx);
nel = idx;
b(1:idx,1) = linspace (base, 7/8 * x(idx) + 1/8, nel);
b(idx:n,1) = 7/8 * x(idx:n) + 1/8;
map = [r, g, b];
else
map = zeros (0, 3);
endif
endfunction
%!demo
%! ## Show the 'bone' colormap profile and as an image
%! cmap = bone (256);
%! subplot (2, 1, 1);
%! rgbplot (cmap, "composite");
%! subplot (2, 1, 2);
%! rgbplot (cmap);
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