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+## Copyright (C) 2004 Josep Mones i Teixidor
+##
+## 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 2 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, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{flag} = } isrgb (@var{A})
+## Returns true if parameter is a RGB image
+##
+## @code{flag=isrgb(A)} returns 1 if @var{A} is a RGB image and 0 if
+## not.
+##
+## To the decide @code{isrgb} uses the follow algorithm:
+## @itemize @bullet
+## @item
+## If @var{A} is of class double then it checks if all values are
+## between 0 and 1, and if size is m-by-n-by-3.
+## @item
+## If @var{A} is of class uint16, uint8 or logical then it checks is m-by-n-by-3.
+## @end itemize
+##
+## @strong{Compatibility notes:}
+##
+## Information needed on whether MATLAB accepts logical arrays as RGB
+## images (now this functions accepts them if they are m-by-n-by-3 arrays.
+##
+## @end deftypefn
+
+## TODO: Check if logical arrays should be considered RGB
+
+## Author:  Josep Mones i Teixidor <jmones@puntbarra.com>
+
+function flag = isrgb(A)
+  if (nargin!=1)
+    usage("flag=isrgb(A)");
+  endif
+  
+  if(ismatrix(A))
+    flag=1;
+    s=size(A);
+    if(length(s)!=3 || s(3)!=3)
+      flag=0; ## false if not m-by-n-by-3
+    elseif(strcmp(typeinfo(A),"matrix") && (any(A(:)<0) || any(A(:)>1)))
+      flag=0; ## false if class double but items are <0 or >1
+    endif
+  else
+    flag=0;
+  endif
+endfunction
+
+
+%!demo
+%! isrgb(rand(1,2,3))
+%! # A 1-by-2-by-3 double matrix with elements between 0 and 1 is a RGB image.
+
+
+%!# Non-matrix
+%!assert(isrgb("this is not a RGB image"),0);
+
+%!# Double matrix tests
+%!assert(isrgb(rand(5,5)),0);
+%!assert(isrgb(rand(5,5,1,5)),0);
+%!assert(isrgb(rand(5,5,3,5)),0);
+%!assert(isrgb(rand(5,5,3)),1);
+%!assert(isrgb(ones(5,5,3)),1);
+%!assert(isrgb(ones(5,5,3)+.0001),0);
+%!assert(isrgb(zeros(5,5,3)-.0001),0);
+
+%!# Logical
+%!assert(isrgb(logical(round(rand(5,5,3)))),1);