update packages

[CreaPhase.git] / octave_packages / m / image / contrast.m

diff --git a/octave_packages/m/image/contrast.m b/octave_packages/m/image/contrast.m
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+## Copyright (C) 2008-2012 David Bateman
+##
+## 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
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} contrast (@var{x}, @var{n})
+## Return a gray colormap that maximizes the contrast in an image.  The
+## returned colormap will have @var{n} rows.  If @var{n} is not defined
+## then the size of the current colormap is used instead.
+## @seealso{colormap}
+## @end deftypefn
+
+function map = contrast (x, n)
+
+  if (nargin == 1)
+    n = rows (colormap);
+  elseif (nargin == 2)
+    if (! isscalar (n))
+      error ("contrast: N must be a scalar");
+    endif
+  else
+    print_usage ();
+  endif
+
+  x = x(:);
+  minx = min (x);
+  map = find (diff (sort ([round(n * ((x - minx) ./ (max(x) - minx))); [0:n]'])));
+  minm = min (map);
+  map = (map - minm) ./ (max (map) - minm);
+  map = [map, map, map];
+endfunction
+
+%!assert (contrast(1:100,10),[([0:9]/9)',([0:9]/9)',([0:9]/9)'],1e-10)
+%!demo
+%! image (reshape (1:100, 10, 10))
+%! colormap (contrast (1:100,10))