1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
########################################################################
##
## Copyright (C) 2012-2024 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} =} colorcube ()
## @deftypefnx {} {@var{map} =} colorcube (@var{n})
## Create color colormap. This colormap is composed of as many equally
## spaced colors (not grays) in the RGB color space as possible.
##
## If there are not a perfect number @var{n} of regularly spaced colors then
## the remaining entries in the colormap are gradients of pure red, green,
## blue, and gray.
##
## 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 = colorcube (n)
if (nargin == 0)
n = rows (colormap);
elseif (! isscalar (n))
error ("colorcube: N must be a scalar");
endif
if (n < 9)
map = gray (n);
return;
endif
## Create colorcube of evenly spaced points with side length of n^1/3
cubelen = fix (cbrt (n));
reserve = n - cubelen^3;
if (reserve == 0)
## Steal space from blue to put the gray gradient
[r, g, b] = meshgrid (linspace (0,1,cubelen),
linspace (0,1,cubelen),
linspace (0,1,cubelen-1));
else
[r, g, b] = meshgrid (linspace (0,1,cubelen),
linspace (0,1,cubelen),
linspace (0,1,cubelen));
endif
## Create map and weed out grays
map = [r(:), g(:), b(:)];
idx = any (bsxfun (@ne, map(:, 1), map(:, 2:3)), 2);
map = map(idx, :);
## Weed out pure colors
idx = sum (map == 0, 2);
map = map(idx != 2, :);
## Put in remaining gradients of pure red, green, blue, and gray
reserve = n - rows (map) - 1;
csteps = fix (reserve/4);
cstepsz = 1 / csteps;
cgrad = (cstepsz:cstepsz:1)';
gsteps = reserve - 3*csteps;
gstepsz = 1 / gsteps;
ggrad = (gstepsz:gstepsz:1)';
map = [map
cgrad, zeros(csteps, 1), zeros(csteps, 1)
zeros(csteps, 1), cgrad, zeros(csteps, 1)
zeros(csteps, 1), zeros(csteps, 1), cgrad
0, 0, 0
ggrad, ggrad, ggrad];
endfunction
%!demo
%! ## Show the 'colorcube' colormap as an image
%! image (1:64, linspace (0, 1, 64), repmat ((1:64)', 1, 64));
%! axis ([1, 64, 0, 1], "xy");
%! set (gca, "xtick", []);
%! colormap (colorcube (64));
|
