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scripts/image/contrast.m

changeset 10289: 4b124317dc38
parent:1bf0ce0930be
author: John W. Eaton <jwe@octave.org>
date: Tue Feb 09 20:58:55 2010 -0500 (32 minutes ago)
permissions: -rw-r--r--
description: base_properties::set_children: account for hidden children 
     1## Copyright (C) 2008, 2009 David Bateman

     2##

     3## This file is part of Octave.

     4##

     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.

     9##

    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.

    14##

    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/>.

    18

    19## -*- texinfo -*-

    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.

    24## @seealso{colormap}

    25## @end deftypefn

    26

    27function map = contrast (x, n)

    28

    29  if (nargin == 1)

    30    n = rows (colormap);

    31  elseif (nargin == 2)

    32    if (! isscalar (n))

    33      error ("contrast: n must be a scalar");

    34    endif

    35  else

    36    print_usage ();

    37  endif

    38

    39  x = x(:);

    40  minx = min (x);

    41  map = find (diff (sort ([round(n * ((x - minx) ./ (max(x) - minx))); [0:n]'])));

    42  minm = min (map);

    43  map = (map - minm) ./ (max (map) - minm);

    44  map = [map, map, map];

    45endfunction

    46

    47%!assert (contrast(1:100,10),[([0:9]/9)',([0:9]/9)',([0:9]/9)'],1e-10)

    48%!demo

    49%! image (reshape (1:100, 10, 10))

    50%! colormap (contrast (1:100,10))