Mercurial > octave-nkf
view scripts/image/contrast.m @ 15683:806ea52af230
Overhaul m-files in image directory to provide better support for images stored as integers.
* NEWS: Add note about overhaul of image scripts to support integer
classes.
* brighten.m: Add demo.
* colormap.m: Better input validation.
* contrast.m: Re-position window in demo.
* gray2ind.m: Redo docstring. Match variables in docstring to function
prototype. Better input validation. Return integer class outputs as
Matlab does. Add %!tests.
* hsv2rgb.m: Add to docstring. Better input validation. Redo algorithm
to get rido of obsolete matrix-fill methods like kron(). Add %!tests.
* image.m: Redo docstring. Match variables in docstring to function
prototype. Better input validation without using for loops.
* imagesc.m: Redo docstring. Match variables in docstring to function
prototype. Remove DEPRECATEDZOOM functionality. Add demos.
* imfinfo.m: Redo docstring.
* ind2gray.m: Redo docstring. Match variables in docstring to function
prototype. Redo algorithm to directly calculate luminance value rather
than getting it from rgb2ntsc. Add %!tests.
* ind2rgb.m: Redo docstring. Better input validation. Add some %!tests.
* ntsc2rgb.m: Redo docstring. Better input validation. Add %!tests.
* rgb2hsv.m: Better input validation. Add %!tests.
* rgb2ind.m: Better input validation. Code algorithm in cleaner method
for ease of understanding.
* rgb2ntsc.m: Redo docstring: Better input validation. Add some %!tests.
author | Rik <rik@octave.org> |
---|---|
date | Tue, 27 Nov 2012 16:38:13 -0800 |
parents | 1f911333ed3d |
children | b1cd65881592 |
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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} {@var{map} =} contrast (@var{x}) ## @deftypefnx {Function File} {@var{map} =} 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 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 %!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)