update packages

[CreaPhase.git] / octave_packages / m / image / prism.m

diff --git a/octave_packages/m/image/prism.m b/octave_packages/m/image/prism.m
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+## Copyright (C) 1999-2012 Kai Habel
+##
+## This file is part of Octave.
+##
+## Octave 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.
+##
+## Octave 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 Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {@var{map} =} prism ()
+## @deftypefnx {Function File} {@var{map} =} prism (@var{n})
+## Create color colormap.  This colormap cycles through red, orange, yellow,
+## green, blue and violet with each index change.
+## The argument @var{n} must be a scalar.
+## If unspecified, the length of the current colormap, or 64, is used.
+## @seealso{colormap}
+## @end deftypefn
+
+## Author:  Kai Habel <kai.habel@gmx.de>
+
+function map = prism (n)
+
+  if (nargin == 0)
+    n = rows (colormap);
+  elseif (nargin == 1)
+    if (! isscalar (n))
+      error ("prism: argument must be a scalar");
+    endif
+  else
+    print_usage ();
+  endif
+
+  p = [1, 0, 0; 1, 1/2, 0; 1, 1, 0; 0, 1, 0; 0, 0, 1; 2/3, 0, 1];
+
+  if (rem (n, 6) == 0)
+    map = kron(ones (fix (n / 6), 1), p);
+  else
+    map = [kron(ones (fix (n / 6), 1), p); p(1:rem (n, 6), :)];
+  endif
+
+endfunction
+
+%!demo
+%! ## Show the 'prism' colormap as an image
+%! image (1:64, linspace (0, 1, 64), repmat (1:64, 64, 1)')
+%! axis ([1, 64, 0, 1], "ticy", "xy")
+%! colormap (prism (64))
+