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colormap: remove functionality to list and register colormaps (bug #48272) * colormap.m: remove the unused functionality which clashes with the possibility of having a colormap named list. It's also not that useful since there's no requirement to register a colormap, and therefore no guarantees that the list is complete. * autumn.m, bone.m, cool.m, copper.m, cubehelix.m, flag.m, gray.m, hot.m, hsv.m, jet.m, lines.m, ocean.m, pink.m, prism.m, rainbow.m, spring.m, summer.m, viridis.m, white.m, winter.m: remove registration to colormap().
author Carnë Draug <carandraug@octave.org>
date Mon, 20 Jun 2016 18:24:18 +0100
parents ffad2baa90f7
children 1c4cd12987f5
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1 ## Copyright (C) 2014-2015 Carnë Draug
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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 3 of the License, or (at
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8 ## your option) 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, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## -*- texinfo -*-
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20 ## @deftypefn {} {@var{map} =} cubehelix ()
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21 ## @deftypefnx {} {@var{map} =} cubehelix (@var{n})
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22 ## Create cubehelix colormap.
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23 ##
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24 ## This colormap varies from black to white going though blue, green, and red
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25 ## tones while maintaining a monotonically increasing perception of intensity.
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26 ## This is achieved by traversing a color cube from black to white through
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27 ## a helix, hence the name cubehelix, while taking into account the perceived
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28 ## brightness of each channel according to the NTSC specifications from 1953.
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29 ##
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30 ## @example
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31 ## rgbplot (cubehelix (256))
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32 ## @end example
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33 ##
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34 ## The argument @var{n} must be a scalar.
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35 ## If unspecified, the length of the current colormap, or 64, is used.
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36 ##
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37 ## Reference: Green, D. A., 2011,
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38 ## @cite{"A @nospell{colour} scheme for the display of astronomical intensity
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39 ## images"}, Bulletin of the Astronomical Society of India, 39, 289.
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40 ##
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41 ## @seealso{colormap}
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42 ## @end deftypefn
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43
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44 ## Author: Carnë Draug <carandraug@octave.org>
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45
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46 function map = cubehelix (n = rows (colormap ()), start = 0.5,
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47 rots = -1.5, hue = 1, gamma = 1)
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48
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49 if (nargin > 5)
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50 print_usage ();
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51 elseif (! isscalar (n))
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52 error ("cubehelix: N must be a scalar");
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53 endif
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54
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55 n = double (n);
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56 if (n > 1)
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57 coeff = [ -0.14861 -0.29227 1.97294
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58 1.78277 -0.90649 0.00000];
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59
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60 fract = ((0:n-1) / (n-1))';
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61 angle = 2 * pi * (start/3 + 1 + rots*fract);
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62 fract .^= gamma;
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63 amp = hue * fract .* (1-fract) /2;
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64 map = fract + amp .* ([cos(angle) sin(angle)] * coeff);
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65
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66 ## Clip values (only in case users have changed values of hue or gamma)
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67 map(map < 0) = 0;
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68 map(map > 1) = 1;
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69 elseif (n > 0)
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70 map = [0, 0, 0];
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71 else
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72 map = zeros (0, 3);
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73 endif
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74
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75 endfunction
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76
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77
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78 ## A better demo of this colormap would be a 3D plot in NTSC instead of
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79 ## RGB values. That would really show what this colormap is about.
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80 %!demo
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81 %! ## Show the 'cubehelix' colormap profile and as an image
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82 %! cmap = cubehelix (256);
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83 %! subplot (2, 1, 1);
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84 %! rgbplot (cmap, "composite");
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85 %! subplot (2, 1, 2);
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86 %! rgbplot (cmap);
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87