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[CreaPhase.git] / octave_packages / m / image / rainbow.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} =} rainbow ()
+## @deftypefnx {Function File} {@var{map} =} rainbow (@var{n})
+## Create color colormap.  This colormap ranges from red through orange,
+## yellow, green, blue, to violet.
+## 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>
+
+## this colormap is not part of matlab, it is like the prism
+## colormap map but with a continuous map
+
+function map = rainbow (n)
+
+  if (nargin == 0)
+    n = rows (colormap);
+  elseif (nargin == 1)
+    if (! isscalar (n))
+      error ("rainbow: argument must be a scalar");
+    endif
+  else
+    print_usage ();
+  endif
+
+  if (n == 1)
+    map = [1, 0, 0];
+  elseif (n > 1)
+    x = linspace (0, 1, n)';
+    r = (x < 2/5) + (x >= 2/5 & x < 3/5) .* (-5 * x + 3)\
+      + (x >= 4/5) .* (10/3 * x - 8/3);
+    g = (x < 2/5) .* (5/2 * x) + (x >= 2/5 & x < 3/5)\
+      + (x >= 3/5 & x < 4/5) .* (-5 * x + 4);
+    b = (x >= 3/5 & x < 4/5) .* (5 * x - 3) + (x >= 4/5);
+    map = [r, g, b];
+  else
+    map = [];
+  endif
+
+endfunction
+
+%!demo
+%! ## Show the 'rainbow' colormap as an image
+%! image (1:64, linspace (0, 1, 64), repmat (1:64, 64, 1)')
+%! axis ([1, 64, 0, 1], "ticy", "xy")
+%! colormap (rainbow (64))
+