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1 ## Copyright (C) 1999, 2000, 2001, 2002, 2004, 2005, 2006, 2007 |
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2 ## Kai Habel |
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3 ## |
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4 ## This file is part of Octave. |
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5 ## |
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6 ## Octave is free software; you can redistribute it and/or modify it |
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7 ## under the terms of the GNU General Public License as published by |
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8 ## the Free Software Foundation; either version 3 of the License, or (at |
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9 ## your option) any later version. |
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10 ## |
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11 ## Octave is distributed in the hope that it will be useful, but |
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 ## General Public License for more details. |
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15 ## |
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16 ## You should have received a copy of the GNU General Public License |
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17 ## along with Octave; see the file COPYING. If not, see |
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18 ## <http://www.gnu.org/licenses/>. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {@var{rgb_map} =} hsv2rgb (@var{hsv_map}) |
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22 ## Transform a colormap or image from the hsv space to the rgb space. |
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23 ## @seealso{rgb2hsv} |
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24 ## @end deftypefn |
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25 |
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26 ## Author: Kai Habel <kai.habel@gmx.de> |
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27 ## Adapted-by: jwe |
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28 |
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29 function rgb_map = hsv2rgb (hsv_map) |
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30 |
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31 ## each color value x=(r,g,b) is calculated with |
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32 ## x = (1-sat)*val+sat*val*f_x(hue) |
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33 ## where f_x(hue) is a piecewise defined function for |
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34 ## each color with f_r(hue-2/3) = f_g(hue) = f_b(hue-1/3) |
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35 |
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36 if (nargin != 1) |
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37 print_usage (); |
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38 endif |
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39 |
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40 ## If we have an image convert it into a color map. |
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41 if (ismatrix (hsv_map) && ndims (hsv_map) == 3) |
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42 is_image = true; |
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43 Sz = size (hsv_map); |
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44 hsv_map = [hsv_map(:,:,1)(:), hsv_map(:,:,2)(:), hsv_map(:,:,3)(:)]; |
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45 ## Convert to a double image. |
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46 if (isinteger (hsv_map)) |
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47 C = class (hsv_map); |
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48 low = double (intmin (C)); |
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49 high = double (intmax (C)); |
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50 hsv_map = (double (hsv_map) - low) / (high - low); |
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51 endif |
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52 else |
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53 is_image = false; |
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54 endif |
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55 |
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56 if (! ismatrix (hsv_map) || columns (hsv_map) != 3) |
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57 error ("hsv2rgb: argument must be a matrix of size nx3"); |
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58 endif |
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59 |
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60 ## set values <0 to 0 and >1 to 1 |
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61 hsv_map = (hsv_map >= 0 & hsv_map <= 1) .* hsv_map \ |
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62 + (hsv_map < 0) .* 0 + (hsv_map > 1); |
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63 |
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64 ## fill rgb map with v*(1-s) |
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65 rgb_map = kron ([1, 1, 1], hsv_map(:,3) .* (1 - hsv_map(:,2))); |
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66 |
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67 ## red(hue-2/3)=green(hue)=blue(hue-1/3) |
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68 ## apply modulo 1 for red and blue |
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69 t = hsv_map(:,1); |
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70 tp = t'; |
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71 hue = [(tp - 2/3 - floor (t - 2/3)'); |
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72 tp; |
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73 (tp - 1/3 - floor (t - 1/3)')]'; |
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74 |
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75 ## factor s*v -> f |
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76 f = kron ([1, 1, 1], hsv_map(:,2)) .* kron ([1, 1, 1], hsv_map(:,3)); |
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77 |
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78 ## add s*v* hue-function to rgb map |
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79 rgb_map = rgb_map + f .* (6 * (hue < 1/6) .* hue |
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80 + (hue >= 1/6 & hue < 1/2) |
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81 + (hue >= 1/2 & hue < 2/3) .* (4 - 6 * hue)); |
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82 |
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83 ## If input was an image, convert it back into one. |
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84 if (is_image) |
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85 rgb_map = reshape (rgb_map, Sz); |
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86 endif |
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87 |
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88 endfunction |
