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diff --git a/octave_packages/m/image/rgb2hsv.m b/octave_packages/m/image/rgb2hsv.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{hsv_map} =} rgb2hsv (@var{rgb})
+## Transform a colormap or image from the RGB space to the HSV space.
+##
+## A color in 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 wavelength.
+## Saturation is the amount of hue mixed into the color.
+## @seealso{hsv2rgb}
+## @end deftypefn
+
+## Author: Kai Habel <kai.habel@gmx.de>
+## Adapted-by: jwe
+
+function hsv_map = rgb2hsv (rgb)
+
+  if (nargin != 1)
+    print_usage ();
+  endif
+
+  ## If we have an image convert it into a color map.
+  if (ismatrix (rgb) && ndims (rgb) == 3)
+    is_image = true;
+    Sz = size (rgb);
+    rgb = [rgb(:,:,1)(:), rgb(:,:,2)(:), rgb(:,:,3)(:)];
+    ## Convert to a double image.
+    if (isinteger (rgb))
+      C = class (rgb);
+      low = double (intmin (C));
+      high = double (intmax (C));
+      rgb = (double (rgb) - low) / (high - low);
+    endif
+  else
+    is_image = false;
+  endif
+
+  if (! ismatrix (rgb) || columns (rgb) != 3)
+    error ("rgb2hsv: RGB_MAP must be a matrix of size n x 3");
+  endif
+
+  ## get the max and min
+  s = min (rgb')';
+  v = max (rgb')';
+
+  ## set hue to zero for undefined values (gray has no hue)
+  h = zeros (size (v));
+  notgray = (s != v);
+
+  ## blue hue
+  idx = (v == rgb(:,3) & notgray);
+  if (any (idx))
+    h(idx) = 2/3 + 1/6 * (rgb(idx,1) - rgb(idx,2)) ./ (v(idx) - s(idx));
+  endif
+
+  ## green hue
+  idx = (v == rgb(:,2) & notgray);
+  if (any (idx))
+    h(idx) = 1/3 + 1/6 * (rgb(idx,3) - rgb(idx,1)) ./ (v(idx) - s(idx));
+  endif
+
+  ## red hue
+  idx = (v == rgb(:,1) & notgray);
+  if (any (idx))
+    h(idx) =       1/6 * (rgb(idx,2) - rgb(idx,3)) ./ (v(idx) - s(idx));
+  endif
+
+  ## correct for negative red
+  idx = (h < 0);
+  h(idx) = 1+h(idx);
+
+  ## set the saturation
+  s(! notgray) = 0;
+  s(notgray) = 1 - s(notgray) ./ v(notgray);
+
+  hsv_map = [h, s, v];
+
+  ## If input was an image, convert it back into one.
+  if (is_image)
+    hsv_map = reshape (hsv_map, Sz);
+  endif
+
+endfunction