Mercurial > hg > octave-image

annotate inst/bwarea.m @ 897:d3ec45cd8660 stable release-2.2.2

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maint: release 2.2.2.
author Carnë Draug <carandraug@octave.org>
date Mon, 06 Oct 2014 17:16:02 +0100
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1 ## Copyright (C) 2005 Søren Hauberg <soren@hauberg.org>
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2 ##
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3 ## This program is free software; you can redistribute it and/or modify it under
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4 ## the terms of the GNU General Public License as published by the Free Software
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5 ## Foundation; either version 3 of the License, or (at your option) any later
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6 ## version.
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7 ##
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8 ## This program is distributed in the hope that it will be useful, but WITHOUT
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9 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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10 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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11 ## details.
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12 ##
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13 ## You should have received a copy of the GNU General Public License along with
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14 ## this program; if not, see <http://www.gnu.org/licenses/>.
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16 ## -*- texinfo -*-
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17 ## @deftypefn {Function File} {@var{total} =} bwarea (@var{bw})
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18 ## Estimate total area of objects on the image @var{bw}.
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19 ##
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20 ## The image @var{bw} can be of any class, even non-logical, in which case non
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21 ## zero valued pixels are considered to be an object.
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22 ##
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23 ## This algorithm is not the same as counting the number of pixels belonging to
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24 ## an object as it tries to estimate the area of the original object. The value
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25 ## of each pixel to the total area is weighted in relation to its neighbour
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26 ## pixels.
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27 ##
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28 ## @seealso{im2bw, bweuler, bwperim, regionprops}
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29 ## @end deftypefn
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31 function total = bwarea (bw)
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32 if (nargin != 1)
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33 print_usage;
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34 elseif (!isimage (bw) || ndims (bw) != 2)
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35 error("bwarea: input image must be a 2D image");
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36 elseif (!islogical (bw))
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37 bw = (bw != 0)
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38 endif
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39
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40 four = ones (2);
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41 two = diag ([1 1]);
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43 fours = conv2 (bw, four);
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44 twos = conv2 (bw, two);
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46 nQ1 = sum (fours(:) == 1);
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47 nQ3 = sum (fours(:) == 3);
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48 nQ4 = sum (fours(:) == 4);
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49 nQD = sum (fours(:) == 2 & twos(:) != 1);
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50 nQ2 = sum (fours(:) == 2 & twos(:) == 1);
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52 total = 0.25*nQ1 + 0.5*nQ2 + 0.875*nQ3 + nQ4 + 0.75*nQD;
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53
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54 endfunction