/usr/share/octave/packages/image-2.2.2/isrgb.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 | ## Copyright (C) 2000 Kai Habel <kai.habel@gmx.de>
## Copyright (C) 2004 Josep Mones i Teixidor <jmones@puntbarra.com>
## Copyright (C) 2011 Carnë Draug <carandraug+dev@gmail.com>
##
## 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} {} isrgb (@var{img})
## Return true if @var{img} is a RGB image.
##
## A variable can be considered a RGB image if it is a non-sparse
## matrix of size @nospell{MxNx3xK} and:
##
## @itemize @bullet
## @item is of class double and all values are in the range [0, 1] or NaN;
## @item is of class uint8, or uint16.
## @end itemize
##
## @strong{Note:} despite their suggestive names, the functions isbw,
## isgray, isind, and isrgb, are ambiguous since it is not always possible
## to distinguish between those image types. For example, an uint8 matrix
## can be both a grayscale and indexed image. They are good to dismiss
## input as an invalid image type, but not for identification.
##
## @seealso{rgb2gray, rgb2ind, isbw, isgray, isind}
## @end deftypefn
function bool = isrgb (img)
if (nargin != 1)
print_usage;
endif
bool = false;
if (isimage (img) && ndims (img) < 5 && size (img, 3) == 3)
switch (class (img))
case "double"
bool = ispart (@is_double_image, img);
case {"uint8", "uint16"}
bool = true;
endswitch
endif
endfunction
%!# Non-matrix
%!assert(isrgb("this is not a RGB image"),false);
%!# Double matrix tests
%!assert(isrgb(rand(5,5)),false);
%!assert(isrgb(rand(5,5,1,5)),false);
%!assert(isrgb(rand(5,5,3,5)),true);
%!assert(isrgb(rand(5,5,3)),true);
%!assert(isrgb(ones(5,5,3)),true);
%!assert(isrgb(ones(5,5,3)+.0001),false);
%!assert(isrgb(zeros(5,5,3)-.0001),false);
%!assert(isrgb(logical(round(rand(5,5,3)))),false);
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