1 ## Copyright (C) 2008-2012 David Bateman
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
20 ## @deftypefn {Function File} {} contrast (@var{x}, @var{n})
21 ## Return a gray colormap that maximizes the contrast in an image. The
22 ## returned colormap will have @var{n} rows. If @var{n} is not defined
23 ## then the size of the current colormap is used instead.
27 function map = contrast (x, n)
33 error ("contrast: N must be a scalar");
41 map = find (diff (sort ([round(n * ((x - minx) ./ (max(x) - minx))); [0:n]'])));
43 map = (map - minm) ./ (max (map) - minm);
44 map = [map, map, map];
47 %!assert (contrast(1:100,10),[([0:9]/9)',([0:9]/9)',([0:9]/9)'],1e-10)
49 %! image (reshape (1:100, 10, 10))
50 %! colormap (contrast (1:100,10))