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1 ## Copyright (C) 2008 David Bateman |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} contrast (@var{x}, @var{n}) |
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21 ## Return a gray colormap that maximizes the contrast in an image. The |
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22 ## returned colormap will have @var{n} rows. If @var{n} is not defined |
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23 ## then the size of the current colormap is used instead. |
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24 ## @seealso{colormap} |
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25 ## @end deftypefn |
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26 |
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27 function map = contrast (x, n) |
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28 |
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29 if (nargin == 1) |
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30 n = rows (colormap); |
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31 elseif (nargin == 2) |
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32 if (! isscalar (n)) |
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33 error ("contrast: n must be a scalar"); |
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34 endif |
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35 else |
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36 print_usage (); |
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37 endif |
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38 |
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39 x = x(:); |
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40 minx = min (x); |
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41 map = find (diff (sort ([round(n * ((x - minx) ./ (max(x) - minx))); [0:n]']))); |
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42 minm = min (map); |
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43 map = (map - minm) ./ (max (map) - minm); |
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44 map = [map, map, map]; |
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45 endfunction |
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46 |
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47 %!assert (contrast(1:100,10),[([0:9]/9)',([0:9]/9)',([0:9]/9)'],1e-10) |
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48 %!demo |
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49 %! image (reshape (1:100, 10, 10)) |
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50 %! colormap (contrast (1:100,10)) |
