1 ## Copyright (C) 1999-2012 Kai Habel
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
20 ## @deftypefn {Function File} {@var{rgb_map} =} hsv2rgb (@var{hsv_map})
21 ## Transform a colormap or image from the HSV space to the RGB space.
25 ## Author: Kai Habel <kai.habel@gmx.de>
28 function rgb_map = hsv2rgb (hsv_map)
30 ## Each color value x = (r,g,b) is calculated with
31 ## x = (1-sat)*val+sat*val*f_x(hue)
32 ## where f_x(hue) is a piecewise defined function for
33 ## each color with f_r(hue-2/3) = f_g(hue) = f_b(hue-1/3).
39 ## If we have an image convert it into a color map.
40 if (ismatrix (hsv_map) && ndims (hsv_map) == 3)
43 hsv_map = [hsv_map(:,:,1)(:), hsv_map(:,:,2)(:), hsv_map(:,:,3)(:)];
44 ## Convert to a double image.
45 if (isinteger (hsv_map))
47 low = double (intmin (C));
48 high = double (intmax (C));
49 hsv_map = (double (hsv_map) - low) / (high - low);
55 if (! ismatrix (hsv_map) || columns (hsv_map) != 3)
56 error ("hsv2rgb: argument must be a matrix of size nx3");
59 ## set values <0 to 0 and >1 to 1
60 hsv_map = (hsv_map >= 0 & hsv_map <= 1) .* hsv_map \
61 + (hsv_map < 0) .* 0 + (hsv_map > 1);
63 ## fill rgb map with v*(1-s)
64 rgb_map = kron ([1, 1, 1], hsv_map(:,3) .* (1 - hsv_map(:,2)));
66 ## red(hue-2/3)=green(hue)=blue(hue-1/3)
67 ## apply modulo 1 for red and blue
70 hue = [(tp - 2/3 - floor (t - 2/3)');
72 (tp - 1/3 - floor (t - 1/3)')]';
75 f = kron ([1, 1, 1], hsv_map(:,2)) .* kron ([1, 1, 1], hsv_map(:,3));
77 ## add s*v* hue-function to rgb map
78 rgb_map = rgb_map + f .* (6 * (hue < 1/6) .* hue
79 + (hue >= 1/6 & hue < 1/2)
80 + (hue >= 1/2 & hue < 2/3) .* (4 - 6 * hue));
82 ## If input was an image, convert it back into one.
84 rgb_map = reshape (rgb_map, Sz);