Mercurial > octave-nkf
view scripts/image/contrast.m @ 20584:eb9e2d187ed2
maint: Use Octave coding conventions in scripts/ode/private dir.
* AbsRel_Norm.m, fuzzy_compare.m, hermite_quartic_interpolation.m,
integrate_adaptive.m, integrate_const.m, integrate_n_steps.m, kahan.m,
ode_struct_value_check.m, odepkg_event_handle.m, odepkg_structure_check.m,
runge_kutta_45_dorpri.m, starting_stepsize.m:
Wrap long lines to < 80 chars.
Use double quotes rather than single quotes where possible.
Use ';' at end of keywords "return;" and "break;"
Use '##" for stand-alone comments and '#' for end-of-line comments.
Use two spaces after period before starting new sentence.
Use '!' instead of '~' for logical negation.
Use specific form of end (endif, endfor, etc.).
Don't use line continuation marker '...' unless necessary.
author | Rik <rik@octave.org> |
---|---|
date | Sun, 04 Oct 2015 22:18:54 -0700 |
parents | 7503499a252b |
children |
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## Copyright (C) 2008-2015 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} {@var{cmap} =} contrast (@var{x}) ## @deftypefnx {Function File} {@var{cmap} =} 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. ## @seealso{colormap, brighten} ## @end deftypefn function cmap = 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); cmap = find (diff (sort ([round(n * ((x - minx) ./ (max(x) - minx))); [0:n]']))); minm = min (cmap); cmap = (cmap - minm) ./ (max (cmap) - minm); cmap = [cmap, cmap, cmap]; endfunction %!demo %! figure; %! img = reshape (1:100, 10, 10); %! imagesc (img); %! colormap (gray (64)); %! title ("Image with default 64 gray levels"); %! pos = get (gcf, "position"); %! pos(1) += pos(3) + 25; %! figure ("position", pos); %! colormap (contrast (img, 10)); %! imagesc (img); %! title ("Image with contrast enhanced"); %!assert (contrast (1:100,10), [([0:9]/9)',([0:9]/9)',([0:9]/9)'], 1e-10)