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comparison scripts/image/rgb2hsv.m @ 3803:63c75bc3db82

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[project @ 2001-02-28 08:24:40 by jwe]
author jwe
date Wed, 28 Feb 2001 08:24:43 +0000
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children 6b00ac653c0f
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3802:4f1a26a730fd 3803:63c75bc3db82
1 ## Copyright (C) 1999, 2000 Kai Habel
2 ##
3 ## This file is part of Octave.
4 ##
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 2, or (at your option)
8 ## any later version.
9 ##
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
14 ##
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, write to the Free
17 ## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
18 ## 02111-1307, USA.
19
20 ## -*- texinfo -*-
21 ## @deftypefn {Function File} {} @var{hsv_map} = rgb2hsv (@var{rgb_map})
22 ## Transform a colormap from the rgb space to the hsv space.
23 ##
24 ## A color n the RGB space consists of the red, green and blue intensities.
25 ##
26 ## In the HSV space each color is represented by their hue, saturation
27 ## and value (brightness). Value gives the amount of light in the color.
28 ## Hue describes the dominant wavelegth.
29 ## Saturation is the amount of Hue mixed into the color.
30 ## @end deftypefn
31 ## @seealso{hsv2rgb}
32
33 ## Author: Kai Habel <kai.habel@gmx.de>
34 ## Adapted-by: jwe
35
36 function hsval = rgb2hsv (rgb)
37
38 if (nargin != 1)
39 usage ("hsv_map = rgb2hsv (rgb_map)");
40 endif
41
42 if (! is_matrix (rgb) || columns (rgb) != 3)
43 error ("rgb2hsv: argument must be a matrix of size n x 3");
44 endif
45
46 # get saturation and value
47 v = max (rgb');
48 s = (v' > 0) .* (1 .- min (rgb') ./ v)';
49
50 # if v==0 set s to 0 too
51 s(isnan (s)) = 0;
52
53 # subtract minimum and divide trough maximum
54 # to get the bright and saturated colors
55 sc = (rgb - kron ([1, 1, 1], min (rgb')'));
56 sv = sc ./ kron([1, 1, 1], max (sc')');
57
58 # if r=g=b (gray value) set hue to 0
59 sv(isnan (sv)) = 0;
60
61 # hue=f(color) must be splitted into 6 parts
62 # 2 for each color
63
64 # h1(green)
65 tmp = (sv(:, 1) == 1 & sv(:,3) == 0) .* (1/6 * sv(:,2) + eps);
66 # avoid problems with h2(red) since hue(0)==hue(1)
67 h = (tmp < 1/6) .* tmp;
68 # h2(green)
69 h = h + ((h == 0) & sv(:,1) == 0 & sv(:,3) == 1) \
70 .* (-1/6 * sv(:,2) + 2/3 + eps);
71
72 # h1(red)
73 h = h + ((h == 0) & sv(:,2) == 1 & sv(:,3) == 0) \
74 .* (-1/6 * sv(:,1) + 1/3 + eps);
75
76 # h2(red)
77 h = h + ((h == 0) & sv(:,2) == 0 & sv(:,3) == 1) \
78 .* (1/6 * sv(:,1) + 2/3 + eps);
79
80 # h1(blue)
81 h = h + ((h == 0) & sv(:,1) == 1 & sv(:,2) == 0) \
82 .* (-1/6 * sv(:,3) + 1 + eps);
83
84 # h2(blue)
85 h = h + ((h == 0) & sv(:,1) == 0 & sv(:,2) == 1) \
86 .* (1/6 * sv(:,3) + 1/3);
87
88 hsval = [h, s, v'];
89
90 endfunction