/usr/share/octave/packages/image-2.6.1/@strel/getsequence.m is in octave-image 2.6.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 | ## Copyright (C) 2012 Roberto Metere <roberto@metere.it>
## Copyright (C) 2013 Carnë Draug <carandraug@octave.org>
##
## This program 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.
##
## This program 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
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{seq} =} getsequence (@var{se})
## Decompose structuring element.
##
## Returns a strel object @var{se} that can be indexed with @code{()} to obtain
## the decomposed structuring elements that can be used to "rebuild" @var{se}.
##
## Decomposing a structuring element may lead to faster operations by
## replacing a single operation with a large @var{se} (large nhood), with
## multiple operations with smaller @var{se}.
##
## Most functions will automatically perform SE decomposition provided a
## strel object is used (instead of a logical array). This also requires
## that specific shapes are specified instead of @qcode{"arbitrary"}, since
## it may prevent SE decomposition.
##
## @seealso{imdilate, imerode, strel}
## @end deftypefn
function se = getsequence (se)
if (isempty (se.seq))
## guess a square/cube/rectangle/hyperrectangle shape even if shape
## is arbitrary. There's no need to decompose when it's very small
## hence the no bother if numel > 15
if (se.flat && all (se.nhood(:)) && ! isvector (se.nhood) &&
numel (se.nhood) > 15)
nd = ndims (se.nhood);
se.seq = cell (nd, 1);
for idx = 1:nd
vec_size = ones (1, nd);
vec_size(idx) = size (se.nhood, idx);
se.seq{idx} = strel ("arbitrary", true (vec_size));
endfor
elseif (strcmp (se.shape, "octagon") && se.opt.apothem > 0)
persistent octagon_template = get_octagon_template ();
se.seq = repmat (octagon_template, se.opt.apothem /3, 1);
else
se.seq{1,1} = se;
endif
endif
endfunction
function template = get_octagon_template ()
template = repmat ({false(3)}, 4, 1);
template{1}(2,:) = true;
template{2}(:,2) = true;
template{3}([1 5 9]) = true;
template{4}([3 5 7]) = true;
template = cellfun (@(x) strel ("arbitrary", x), template, "UniformOutput", false);
endfunction
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