1## Copyright (C) 2000 Kai Habel <kai.habel@gmx.de> 2## Copyright (C) 2011, 2015 Carnë Draug <carandraug+dev@gmail.com> 3## 4## This program is free software; you can redistribute it and/or modify 5## it under the terms of the GNU General Public License as published by 6## the Free Software Foundation; either version 3 of the License, or 7## (at your option) any later version. 8## 9## This program is distributed in the hope that it will be useful, 10## but WITHOUT ANY WARRANTY; without even the implied warranty of 11## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12## GNU General Public License for more details. 13## 14## You should have received a copy of the GNU General Public License 15## along with this program; if not, see <http://www.gnu.org/licenses/>. 16 17## -*- texinfo -*- 18## @deftypefn {Function File} {} isgray (@var{img}) 19## Return true if @var{img} is a grayscale image. 20## 21## A variable can be considered a grayscale image if it is a non-sparse, 22## real array of size @nospell{MxNx1xK}, and: 23## 24## @itemize @bullet 25## @item of floating point class with values in the [0 1] range or NaN; 26## @item of class uint8, uint16, or int16. 27## @end itemize 28## 29## @emph{Note}: despite their suggestive names, the functions isbw, 30## isgray, isind, and isrgb, are ambiguous since it is not always possible 31## to distinguish between those image types. For example: an uint8 matrix 32## can be both a grayscale and indexed image; a grayscale image may have 33## values outside the range [0 1]. They are good to dismiss input as an 34## invalid image type, but not for identification. 35## 36## @seealso{gray2ind, isbw, isind, isrgb} 37## @end deftypefn 38 39function bool = isgray (img) 40 if (nargin () != 1) 41 print_usage (); 42 endif 43 44 bool = false; 45 if (isimage (img) && ndims (img) < 5 && size (img, 3) == 1) 46 if (isfloat (img)) 47 bool = ispart (@is_float_image, img); 48 elseif (any (isa (img, {"uint8", "uint16", "int16"}))) 49 bool = true; 50 endif 51 endif 52endfunction 53 54%!assert (isgray ([0 0 1; 1 0 1]), true) 55%!assert (isgray (zeros (3)), true) 56%!assert (isgray (ones (3)), true) 57 58%!test 59%! a = rand (10); 60%! assert (isgray (a), true); 61%! a(5, 5) = 2; 62%! assert (isgray (a), false); 63 64%!test 65%! a = uint8 (randi (255, 10)); 66%! assert (isgray (a), true); 67%! a = int8 (a); 68%! assert (isgray (a), false); 69 70%!test 71%! a = rand (10); 72%! a(50) = NaN; 73%! assert (isgray (a), true); 74 75%!assert (isgray (rand (5, 5, 1, 4)), true); 76%!assert (isgray (rand (5, 5, 3, 4)), false); 77%!assert (isgray (rand (5, 5, 3)), false); 78%!assert (isgray (rand (5, 5, 1, 3, 4)), false); 79 80%!assert (isgray (rand (5, "single")), true) 81 82## While having some NaN is ok, having all NaN is not 83%!assert (isgray ([.1 .2 .3; .4 NaN .6; .7 .8 .9]), true) 84%!assert (isgray ([.1 .2 .3; NA NaN .6; .7 .8 .9]), true) 85%!assert (isgray ([.1 .2 .3; NA .5 .6; .7 .8 .9]), true) 86%!assert (isgray (NaN (5)), false) 87%!assert (isgray (NA (5)), false) 88