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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, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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18 ## 02110-1301, USA. |
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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 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 usage ("rgb_map = hsv2rgb (hsv_map)"); |
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38 endif |
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39 |
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40 if (! ismatrix (hsv_map) || columns (hsv_map) != 3) |
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41 error ("hsv2rgb: argument must be a matrix of size nx3"); |
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42 endif |
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43 |
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44 ## set values <0 to 0 and >1 to 1 |
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45 hsv_map = (hsv_map >= 0 & hsv_map <= 1) .* hsv_map \ |
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46 + (hsv_map < 0) .* 0 + (hsv_map > 1); |
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47 |
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48 ## fill rgb map with v*(1-s) |
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49 rgb_map = kron ([1, 1, 1], hsv_map(:,3) .* (1 - hsv_map(:,2))); |
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50 |
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51 ## red(hue-2/3)=green(hue)=blue(hue-1/3) |
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52 ## apply modulo 1 for red and blue |
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53 t = hsv_map(:,1); |
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54 tp = t'; |
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55 hue = [(tp - 2/3 - floor (t - 2/3)'); |
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56 tp; |
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57 (tp - 1/3 - floor (t - 1/3)')]'; |
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58 |
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59 ## factor s*v -> f |
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60 f = kron ([1, 1, 1], hsv_map(:,2)) .* kron ([1, 1, 1], hsv_map(:,3)); |
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61 |
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62 ## add s*v* hue-function to rgb map |
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63 rgb_map = rgb_map + f .* (6 * (hue < 1/6) .* hue |
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64 + (hue >= 1/6 & hue < 1/2) |
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65 + (hue >= 1/2 & hue < 2/3) .* (4 - 6 * hue)); |
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66 |
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67 endfunction |
