/usr/share/octave/packages/image-2.4.1/mat2gray.m is in octave-image 2.4.1-1.
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 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 | ## Copyright (C) 1999, 2000 Kai Habel <kai.habel@gmx.de>
## Copyright (C) 2011, 2012 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} {@var{I} =} mat2gray (@var{M})
## @deftypefnx {Function File} {@var{I} =} mat2gray (@var{M}, [@var{min} @var{max}])
## Convert a matrix to an intensity image.
##
## The returned matrix @var{I} is a grayscale image, of double class and in the
## range of values [0, 1]. The optional arguments @var{min} and @var{max} will
## set the limits of the conversion; values in @var{M} below @var{min} and
## above @var{max} will be set to 0 and 1 on @var{I} respectively.
##
## @var{max} and @var{min} default to the maximum and minimum values of @var{M}.
##
## If @var{min} is larger than @var{max}, the `inverse' will be returned. Values
## in @var{M} above @var{max} will be set to 0 while the ones below @var{min}
## will be set to 1.
##
## @strong{Caution:} For compatibility with @sc{matlab}, if @var{min} and @var{max}
## are equal (either from being actually being set manually or automatically
## calculated from the @var{M} min and max values, Octave's mat2gray will truncate
## all values between [0 1]. For example
##
## @example
## @group
## mat2gray ([-2 0 0.5 0.9 5], [2 2])
## @result{} [0 0 0.5 0.9 1]
## mat2gray ([0.5 0.5 0.5])
## @result{} [0.5 0.5 0.5]
## mat2gray ([4 4 4])
## @result{} [1 1 1]
## @end group
## @end example
##
## @seealso{gray2ind, ind2gray, rgb2gray, im2double, im2uin16, im2uint8, im2int16}
## @end deftypefn
function in = mat2gray (in, scale)
if (nargin < 1 || nargin > 2)
print_usage;
elseif (! isnumeric (in) && ! islogical (in))
error ("mat2gray: IN must be a matrix");
elseif (nargin == 2 && (!isvector (scale) || numel (scale) != 2))
error ("mat2gray: second argument must be a vector with 2 elements");
endif
if (nargin == 1)
out_min = min (in(:));
out_max = max (in(:));
else
## see more at the end for the cases where max and min are swapped
out_min = min (scale (1), scale (2));
out_max = max (scale (1), scale (2));
endif
## since max() and min() return a value of same class as input,
## need to make this values double or the calculations later may fail
out_min = double (out_min);
out_max = double (out_max);
## if max and min are the same, matlab seems to simple truncate the input
## between 0 and 1, and ignores the min/max values set. Don't get the logic
## but hey! Matlab compatibility
if (out_min == out_max)
in(in>1) = 1;
in(in<0) = 0;
return
endif
## we are editing the input matrix rather than creating a new one to save
## memory. We need to make sure it's double though
in = double(in);
## it's faster to get the index of values between max and min only once
## than to have it calculated on both sides of the assignment later on. We
## need to get the index before starting editing
idx = (in > out_min & in < out_max);
in(in <= out_min) = 0;
in(in >= out_max) = 1;
in(idx) = (1/(out_max - out_min)) * (double(in(idx)) - out_min);
## if the given min and max are in the inverse order...
if (nargin > 1 && scale(1) > scale (2))
## matlab seems to allow setting the min higher than the max but not by
## checking which one is actually correct. Seems to just invert it
in = abs (in - 1);
endif
endfunction
%!assert(mat2gray([1 2 3]), [0 0.5 1]); # standard use
%!assert(mat2gray(repmat ([1 2; 3 3], [1 1 3])), repmat ([0 0.5; 1 1], [1 1 3])); # setting min and max
%!assert(mat2gray([1 2 3], [2 2]), [1 1 1]); # equal min and max
%!assert(mat2gray([-1 0 0.5 3], [2 2]), [0 0 0.5 1]); # equal min and max
%!assert(mat2gray(ones(3*0.5)), ones(3*0.5)); # equal min and max from the image (not set)
%!assert(mat2gray([1 2 3], [3 1]), [1 0.5 0]); # max and min inverted
|