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+## 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, 59 Temple Place - Suite 330, Boston, MA
+## 02111-1307, USA.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} @var{hsv_map} = rgb2hsv (@var{rgb_map})
+## Transform a colormap from the rgb space to the hsv space.
+##
+## A color n the RGB space consists of the red, green and blue intensities.
+##
+## In the HSV space each color is represented by their hue, saturation
+## and value (brightness).  Value gives the amount of light in the color.
+## Hue describes the dominant wavelegth. 
+## Saturation is the amount of Hue mixed into the color. 
+## @end deftypefn
+## @seealso{hsv2rgb}
+
+## Author: Kai Habel <kai.habel@gmx.de>
+## Adapted-by: jwe
+
+function hsval = rgb2hsv (rgb)
+
+  if (nargin != 1)
+    usage ("hsv_map = rgb2hsv (rgb_map)");
+  endif
+
+  if (! is_matrix (rgb) || columns (rgb) != 3)
+    error ("rgb2hsv: argument must be a matrix of size n x 3");
+  endif
+
+  # get saturation and value
+  v = max (rgb');
+  s = (v' > 0) .* (1 .- min (rgb') ./ v)';
+
+  # if v==0 set s to 0 too
+  s(isnan (s)) = 0;
+
+  # subtract minimum and divide trough maximum
+  # to get the bright and saturated colors
+  sc = (rgb - kron ([1, 1, 1], min (rgb')'));
+  sv = sc ./ kron([1, 1, 1], max (sc')');
+
+  # if r=g=b (gray value) set hue to 0
+  sv(isnan (sv)) = 0;
+
+  # hue=f(color) must be splitted into 6 parts 
+  # 2 for each color
+
+  # h1(green)
+  tmp = (sv(:, 1) == 1 & sv(:,3) == 0) .* (1/6 * sv(:,2) + eps);
+  # avoid problems with h2(red) since hue(0)==hue(1)
+  h = (tmp < 1/6) .* tmp; 
+  # h2(green)
+  h = h + ((h == 0) & sv(:,1) == 0 & sv(:,3) == 1) \
+      .* (-1/6 * sv(:,2) + 2/3 + eps);
+
+  # h1(red)
+  h = h + ((h == 0) & sv(:,2) == 1 & sv(:,3) == 0) \
+      .* (-1/6 * sv(:,1) + 1/3 + eps);
+
+  # h2(red)
+  h = h + ((h == 0) & sv(:,2) == 0 & sv(:,3) == 1) \
+      .* (1/6 * sv(:,1) + 2/3 + eps);
+
+  # h1(blue)
+  h = h + ((h == 0) & sv(:,1) == 1 & sv(:,2) == 0) \
+      .* (-1/6 * sv(:,3) + 1 + eps);
+
+  # h2(blue)
+  h = h + ((h == 0) & sv(:,1) == 0 & sv(:,2) == 1) \
+      .* (1/6 * sv(:,3) + 1/3);
+
+  hsval = [h, s, v'];
+
+endfunction