Mercurial > octave-nkf
annotate scripts/image/hot.m @ 16466:ac332eb727dd
Simplify calculation of colormaps
* scripts/image/copper.m: Replace slower linspace with range operator.
* scripts/image/hot.m: Add test for n==2 to allow elimination of subsequent
if conditional tests. Replace mod calculation with simpler expression.
* scripts/image/rainbow.m: Replace slower linspace with range operator.
Align columns of calculation for better code readability.
author | Rik <rik@octave.org> |
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date | Sun, 07 Apr 2013 22:24:34 -0700 |
parents | 6964e6b92fc1 |
children | d63878346099 |
rev | line source |
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maint: update copyright notices for 2012
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1 ## Copyright (C) 1999-2012 Kai Habel |
6788 | 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 | |
7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
8 ## your option) any later version. | |
6788 | 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 | |
7016 | 16 ## along with Octave; see the file COPYING. If not, see |
17 ## <http://www.gnu.org/licenses/>. | |
6788 | 18 |
19 ## -*- texinfo -*- | |
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20 ## @deftypefn {Function File} {@var{map} =} hot () |
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21 ## @deftypefnx {Function File} {@var{map} =} hot (@var{n}) |
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22 ## Create color colormap. This colormap ranges from black through dark red, |
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23 ## red, orange, yellow, to white. |
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24 ## The argument @var{n} must be a scalar. |
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25 ## If unspecified, the length of the current colormap, or 64, is used. |
6788 | 26 ## @seealso{colormap} |
27 ## @end deftypefn | |
28 | |
29 ## Author: Kai Habel <kai.habel@gmx.de> | |
30 | |
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31 ## PKG_ADD: colormap ("register", "hot"); |
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32 ## PKG_DEL: colormap ("unregister", "hot"); |
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33 |
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34 function map = hot (n) |
6788 | 35 |
36 if (nargin == 0) | |
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37 n = rows (colormap); |
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38 elseif (nargin == 1) |
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39 if (! isscalar (n)) |
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40 error ("hot: N must be a scalar"); |
6788 | 41 endif |
42 else | |
43 print_usage (); | |
44 endif | |
45 | |
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46 if (n == 1) |
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47 map = [1, 1, 1]; |
16466 | 48 elseif (n == 2) |
49 map = [1, 1, 1/2 | |
50 1, 1, 1 ]; | |
51 elseif (n > 2) | |
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52 idx = floor (3/8 * n); |
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53 nel = idx; |
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54 |
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55 r = ones (n, 1); |
16466 | 56 r(1:idx, 1) = [1:nel]' / nel; |
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57 |
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58 g = zeros (n, 1); |
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59 g(idx+1:2*idx, 1) = r(1:idx); |
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60 g(2*idx+1:end, 1) = 1; |
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61 |
16466 | 62 idx = 2*idx + 1; # approximately 3/4 *n |
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63 nel = n - idx + 1; |
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64 |
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65 b = zeros (n, 1); |
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66 b(idx:end, 1) = [1:nel]' / nel; |
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67 |
6788 | 68 map = [r, g, b]; |
69 else | |
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70 map = zeros (0, 3); |
6788 | 71 endif |
72 | |
73 endfunction | |
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74 |
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75 |
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76 %!demo |
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77 %! ## Show the 'hot' colormap as an image |
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78 %! image (1:64, linspace (0, 1, 64), repmat ((1:64)', 1, 64)); |
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79 %! axis ([1, 64, 0, 1], "ticy", "xy"); |
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80 %! colormap (hot (64)); |
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81 |