/usr/share/octave/packages/image-2.2.2/imcomplement.m is in octave-image 2.2.2-1.
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 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 | ## Copyright (C) 2008 Søren Hauberg <soren@hauberg.org>
## Copyright (C) 2014 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} {} imcomplement (@var{A})
## Compute image complement or negative.
##
## Intuitively this corresponds to the intensity of bright and dark
## regions being reversed. The exact operation performed is dependent
## on the class of the image.
##
## @table @asis
## @item floating point
## Since floating point images are meant to have values in the range [0 1],
## this is equivalent @code{A -1}. This leads to values within the range
## to be inverted while others to equally distance from the limits.
##
## @item logical
## Equivalent to @code{! A}
##
## @item integer
## Inverts the values within the range of the data. This is a different
## depending whether it's signed or unsigned integers class.
## @end table
##
## @seealso{imadd, imdivide, imlincomb, immultiply, imsubtract}
## @end deftypefn
function B = imcomplement (A)
if (nargin != 1)
print_usage ();
endif
if (isfloat (A))
B = 1 - A;
elseif (islogical (A))
B = ! A;
elseif (any (isa (A, {"int8", "int16", "int32", "int64"})))
## Signed integers are different. We have all this extra work to avoid
## conversion into another class which may not fit in memory. And seems
## like it it still performs faster.
cl = class (A);
B = zeros (size (A), cl);
m = (A != intmin (cl));
B(! m) = intmax (cl);
B(m) = -A -1;
elseif (isinteger (A))
B = intmax (class (A)) - A;
else
error("imcomplement: A must be an image but is of class `%s'", class (A));
endif
endfunction
%!assert (imcomplement (10), -9);
%!assert (imcomplement (single (10)), single (-9));
%!assert (imcomplement (0.2), 0.8);
%!assert (imcomplement (uint8 (0)), uint8 (255));
%!assert (imcomplement (uint8 (1)), uint8 (254));
%!assert (imcomplement (uint16 (0)), uint16 (65535));
%!assert (imcomplement (uint16 (1)), uint16 (65534));
%!assert (imcomplement (int8 (-128)), int8 ( 127));
%!assert (imcomplement (int8 ( 127)), int8 (-128));
%!assert (imcomplement (int16 (-1)), int16 ( 0));
%!assert (imcomplement (int16 ( 0)), int16 (-1));
%!assert (imcomplement (int16 ( 1)), int16 (-2));
%!assert (imcomplement ([true false true]), [false true false])
%!error <must be an image> imcomplement ("not an image")
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