/usr/share/octave/packages/image-2.6.1/lab2single.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 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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 | ## Copyright (C) 2016 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} {} lab2double (@var{lab})
## Convert L*a*b* data to single precision.
##
## @var{lab} must be a L*a*b* image or colormap, i.e., its dimensions
## must be MxNx3xK or Mx3. Its type must be double, single, uint16,
## or uint8.
##
## When converted to single, L* values range from 0 to 100, while a* and
## b* range from -128 to 127. When converting from uint16, the upper limit
## is 65280 (higher values will be converted above the range).
##
## @seealso{lab2double, lab2rgb, lab2single, lab2uint8, lab2uin16, lab2xyz}
## @end deftypefn
function [lab] = lab2single (lab)
if (nargin () != 1)
print_usage ();
endif
lab = lab2cls (lab, "single");
endfunction
## Instead of testing the lab2single function here, we test the
## conversion from single type. The actual tests for lab2single,
## are spread all other lab2* functions. This makes the tests
## simpler.
%!test
%! l_max_f = 100 + (25500 / 65280);
%! ab_max_f = 127 + (255 / 256);
%! cm = [
%! -Inf
%! Inf
%! NaN
%! l_max_f
%! ab_max_f
%! -200
%! -129
%! -128
%! -128+(255/65280)*(0.499)
%! -128+(255/65280)*(0.500)
%! -128+(255/65280)*(0.501)
%! -127
%! -1
%! 0
%! (100/65280)*(0.499999)
%! (100/65280)*(0.51)
%! (100/65280)*(0.500001)
%! 1
%! 99
%! 100
%! 101
%! 126
%! 127
%! 128
%! 254
%! 255
%! 256
%! 257];
%! cm = repmat (single (cm), [1 3]);
%! im2d = reshape (cm, [7 4 3]);
%! imnd = permute (im2d, [1 4 3 2]);
%!
%! cm_uint8 = uint8 ([
%! 0 0 0
%! 255 255 255
%! 255 255 255
%! 255 228 228
%! 255 255 255
%! 0 0 0
%! 0 0 0
%! 0 0 0
%! 0 0 0
%! 0 0 0
%! 0 0 0
%! 0 1 1
%! 0 127 127
%! 0 128 128
%! 0 128 128
%! 0 128 128
%! 0 128 128
%! 3 129 129
%! 252 227 227
%! 255 228 228
%! 255 229 229
%! 255 254 254
%! 255 255 255
%! 255 255 255
%! 255 255 255
%! 255 255 255
%! 255 255 255
%! 255 255 255]);
%!
%! assert (lab2uint8 (cm), cm_uint8)
%! im2d_uint8 = reshape (cm_uint8, [7 4 3]);
%! assert (lab2uint8 (im2d), im2d_uint8)
%! assert (lab2uint8 (imnd), permute (im2d_uint8, [1 4 3 2]))
%!
%! cm_uint16 = uint16 ([
%! 0 0 0
%! 65535 65535 65535
%! 65535 65535 65535
%! 65535 58468 58468
%! 65535 65535 65535
%! 0 0 0
%! 0 0 0
%! 0 0 0
%! 0 0 0
%! 0 1 1
%! 0 1 1
%! 0 256 256
%! 0 32512 32512
%! 0 32768 32768
%! 0 32768 32768
%! 1 32768 32768
%! 1 32768 32768
%! 653 33024 33024
%! 64627 58112 58112
%! 65280 58368 58368
%! 65535 58624 58624
%! 65535 65024 65024
%! 65535 65280 65280
%! 65535 65535 65535
%! 65535 65535 65535
%! 65535 65535 65535
%! 65535 65535 65535
%! 65535 65535 65535]);
%!
%! assert (lab2uint16 (cm), cm_uint16)
%! im2d_uint16 = reshape (cm_uint16, [7 4 3]);
%! assert (lab2uint16 (im2d), im2d_uint16)
%! assert (lab2uint16 (imnd), permute (im2d_uint16, [1 4 3 2]))
%!
%! assert (lab2double (cm), double (cm))
%! assert (lab2double (im2d), double (im2d))
%! assert (lab2double (imnd), double (imnd))
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