Mercurial > hg > octave-nkf
annotate scripts/image/contrast.m @ 20279:db30302bedc3
Added tag rc-4-0-0-3 for changeset 065f933ef083
| author | John W. Eaton <jwe@octave.org> |
|---|---|
| date | Fri, 10 Apr 2015 14:41:21 -0400 |
| parents | 4197fc428c7d |
| children | 7503499a252b |
| rev | line source |
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maint: Update copyright notices for 2015.
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1 ## Copyright (C) 2008-2015 David Bateman |
| 7633 | 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 -*- | |
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20 ## @deftypefn {Function File} {@var{cmap} =} contrast (@var{x}) |
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21 ## @deftypefnx {Function File} {@var{cmap} =} contrast (@var{x}, @var{n}) |
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22 ## Return a gray colormap that maximizes the contrast in an image. The |
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23 ## returned colormap will have @var{n} rows. If @var{n} is not defined |
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24 ## then the size of the current colormap is used. |
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25 ## @seealso{colormap, brighten} |
| 7633 | 26 ## @end deftypefn |
| 27 | |
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28 function cmap = contrast (x, n) |
| 7633 | 29 |
| 30 if (nargin == 1) | |
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31 n = rows (colormap ()); |
| 7633 | 32 elseif (nargin == 2) |
| 33 if (! isscalar (n)) | |
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34 error ("contrast: N must be a scalar"); |
| 7633 | 35 endif |
| 36 else | |
| 37 print_usage (); | |
| 38 endif | |
| 39 | |
| 40 x = x(:); | |
| 41 minx = min (x); | |
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42 cmap = find (diff (sort ([round(n * ((x - minx) ./ (max(x) - minx))); [0:n]']))); |
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43 minm = min (cmap); |
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44 cmap = (cmap - minm) ./ (max (cmap) - minm); |
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45 cmap = [cmap, cmap, cmap]; |
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46 |
| 7633 | 47 endfunction |
| 48 | |
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49 |
| 7633 | 50 %!demo |
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51 %! figure; |
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52 %! img = reshape (1:100, 10, 10); |
| 14253 | 53 %! imagesc (img); |
| 54 %! colormap (gray (64)); | |
| 55 %! title ("Image with default 64 gray levels"); | |
| 56 %! pos = get (gcf, "position"); | |
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57 %! pos(1) += pos(3) + 25; |
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58 %! figure ("position", pos); |
| 14253 | 59 %! colormap (contrast (img, 10)); |
| 60 %! imagesc (img); | |
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61 %! title ("Image with contrast enhanced"); |
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62 |
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63 %!assert (contrast (1:100,10), [([0:9]/9)',([0:9]/9)',([0:9]/9)'], 1e-10) |
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64 |