/usr/share/octave/packages/image-2.2.2/rgb2ycbcr.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) 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{YCbCrmap} =} rgb2ycbcr (@var{cmap})
## @deftypefnx {Function File} {@var{YCbCr} =} rgb2ycbcr (@var{RGB})
## @deftypefnx {Function File} {@dots{} =} rgb2ycbcr (@dots{}, [@var{Kb} @var{Kr}])
## @deftypefnx {Function File} {@dots{} =} rgb2ycbcr (@dots{}, @var{standard})
## Convert RGB values to YCbCr.
##
## The convertion changes the image @var{RGB} or colormap @var{cmap}, from
## the RGB color model to YCbCr (luminance, chrominance blue, and chrominance
## red). @var{RGB} must be of class double, single, uint8, or uint16.
##
## The formula used for the conversion is dependent on two constants, @var{Kb}
## and @var{Kr} which can be specified individually, or according to existing
## standards:
##
## @table @asis
## @item "601" (default)
## According to the ITU-R BT.601 (formerly CCIR 601) standard. Its values
## of @var{Kb} and @var{Kr} are 0.114 and 0.299 respectively.
## @item "709" (default)
## According to the ITU-R BT.709 standard. Its values of @var{Kb} and
## @var{Kr} are 0.0722 and 0.2116 respectively.
## @end table
##
## @seealso{hsv2rgb, ntsc2rgb, rgb2hsv, rgb2ntsc}
## @end deftypefn
function ycbcr = rgb2ycbcr (rgb, standard = "601")
if (nargin < 1 || nargin > 2)
print_usage ();
endif
ycbcr = ycbcrfunc ("rgb2ycbcr", rgb, standard);
endfunction
%!test
%! in(:,:,1) = magic (5);
%! in(:,:,2) = magic (5);
%! in(:,:,3) = magic (5);
%! out(:,:,1) = [31 37 17 23 29
%! 36 20 22 28 30
%! 19 21 27 33 35
%! 25 26 32 34 19
%! 25 31 37 18 24];
%! out(:,:,2) = 128;
%! out(:,:,3) = 128;
%! assert (rgb2ycbcr (uint8 (in)), uint8 (out));
%!shared cbcr
%! cbcr = 0.5019607843137255;
%! out(1:10, 1) = linspace (16/255, 235/255, 10);
%! out(:, [2 3]) = cbcr;
%! assert (rgb2ycbcr (gray (10)), out, 0.00001);
%!assert (rgb2ycbcr ([1 1 1]), [0.92157 cbcr cbcr], 0.0001);
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