--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/image/prism.m	Mon Jul 23 22:05:30 2007 +0000
@@ -0,0 +1,50 @@
+## Copyright (C) 1999,2000  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 2, 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, write to the Free
+## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+## 02110-1301, USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} prism (@var{n})
+## Create color colormap. This colormap cycles trough red, orange, yellow,
+## green, blue and violet. The argument @var{n} should be a scalar.  If it
+## is omitted, the length of the current colormap or 64 is assumed.
+## @seealso{colormap}
+## @end deftypefn
+
+## Author:  Kai Habel <kai.habel@gmx.de>
+
+function map = prism (number)
+
+  if (nargin == 0)
+    number = rows (colormap);
+  elseif (nargin == 1)
+    if (! is_scalar (number))
+      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 (number, 6) == 0)
+    map = kron(ones (fix (number / 6), 1), p);
+  else
+    map = [kron(ones (fix (number / 6), 1), p); p(1:rem (number, 6), :)];
+  endif
+
+endfunction