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1 ## Copyright (C) 1999, 2000 Kai Habel |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 2, or (at your option) |
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8 ## any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, write to the Free |
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17 ## Software Foundation, 59 Temple Place - Suite 330, Boston, MA |
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18 ## 02111-1307, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} @var{hsv_map} = rgb2hsv (@var{rgb_map}) |
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22 ## Transform a colormap from the rgb space to the hsv space. |
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23 ## |
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24 ## A color n the RGB space consists of the red, green and blue intensities. |
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25 ## |
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26 ## In the HSV space each color is represented by their hue, saturation |
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27 ## and value (brightness). Value gives the amount of light in the color. |
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28 ## Hue describes the dominant wavelegth. |
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29 ## Saturation is the amount of Hue mixed into the color. |
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30 ## @end deftypefn |
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31 ## @seealso{hsv2rgb} |
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32 |
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33 ## Author: Kai Habel <kai.habel@gmx.de> |
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34 ## Adapted-by: jwe |
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35 |
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36 function hsval = rgb2hsv (rgb) |
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37 |
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38 if (nargin != 1) |
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39 usage ("hsv_map = rgb2hsv (rgb_map)"); |
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40 endif |
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41 |
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42 if (! is_matrix (rgb) || columns (rgb) != 3) |
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43 error ("rgb2hsv: argument must be a matrix of size n x 3"); |
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44 endif |
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45 |
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46 ## get the max and min |
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47 s = min (rgb')'; |
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48 v = max (rgb')'; |
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49 |
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50 ## set hue to zero for undefined values (gray has no hue) |
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51 h = zeros (size (v)); |
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52 notgray = (s != v); |
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53 |
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54 ## blue hue |
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55 idx = (v == rgb(:,3) & notgray); |
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56 if (any (idx)) |
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57 h(idx) = 2/3 + 1/6 * (rgb(idx,1) - rgb(idx,2)) ./ (v(idx) - s(idx)); |
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58 endif |
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59 |
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60 ## green hue |
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61 idx = (v == rgb(:,2) & notgray); |
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62 if (any (idx)) |
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63 h(idx) = 1/3 + 1/6 * (rgb(idx,3) - rgb(idx,1)) ./ (v(idx) - s(idx)); |
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64 endif |
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65 |
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66 ## red hue |
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67 idx = (v == rgb(:,1) & notgray); |
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68 if (any (idx)) |
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69 h(idx) = 1/6 * (rgb(idx,2) - rgb(idx,3)) ./ (v(idx) - s(idx)); |
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70 endif |
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71 |
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72 ## correct for negative red |
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73 idx = (h < 0); |
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74 h(idx) = 1+h(idx); |
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75 |
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76 ## set the saturation |
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77 s(! notgray) = 0; |
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78 s(notgray) = 1 - s(notgray) ./ v(notgray); |
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79 |
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80 hsval = [h, s, v]; |
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81 |
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82 endfunction |
