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annotate scripts/image/rgb2ntsc.m @ 20654:b65888ec820e draft default tip gccjit

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dmalcom gcc jit import
author Stefan Mahr <dac922@gmx.de>
date Fri, 27 Feb 2015 16:59:36 +0100
parents 131ce8cfaa80
children
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1 ## Copyright (C) 1994-2015 John W. Eaton
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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 {Function File} {@var{yiq_map} =} rgb2ntsc (@var{rgb_map})
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21 ## @deftypefnx {Function File} {@var{yiq_img} =} rgb2ntsc (@var{rgb_img})
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22 ## Transform a colormap or image from red-green-blue (RGB) color space to
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23 ## luminance-chrominance (NTSC) space. The input may be of class uint8,
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24 ## uint16, single, or double. The output is of class double.
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25 ##
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26 ## Implementation Note:
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27 ## The reference matrix for the transformation is
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28 ##
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29 ## @example
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30 ## @group
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31 ## /Y\ 0.299 0.587 0.114 /R\
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32 ## |I| = 0.596 -0.274 -0.322 |G|
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33 ## \Q/ 0.211 -0.523 0.312 \B/
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34 ## @end group
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35 ## @end example
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36 ##
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37 ## @noindent
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38 ## as documented in @url{http://en.wikipedia.org/wiki/YIQ} and truncated to 3
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39 ## significant figures. Note: The FCC version of NTSC uses only 2 significant
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40 ## digits and is slightly different.
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41 ## @seealso{ntsc2rgb, rgb2hsv, rgb2ind}
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42 ## @end deftypefn
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44 ## Author: Tony Richardson <arichard@stark.cc.oh.us>
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45 ## Created: July 1994
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46 ## Adapted-By: jwe
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47
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48 function yiq = rgb2ntsc (rgb)
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49
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50 if (nargin != 1)
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51 print_usage ();
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52 endif
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53
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54 [rgb, cls, sz, is_im, is_nd, is_int] ...
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55 = colorspace_conversion_input_check ("rgb2ntsc", "RGB", rgb);
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56
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57 ## Reference matrix for transformation from http://en.wikipedia.org/wiki/YIQ
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58 ## and truncated to 3 significant figures. Matlab uses this matrix for their
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59 ## conversion.
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60 trans = [ 0.299, 0.596, 0.211;
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61 0.587, -0.274, -0.523;
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62 0.114, -0.322, 0.312 ];
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63 yiq = rgb * trans;
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64
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65 yiq = colorspace_conversion_revert (yiq, cls, sz, is_im, is_nd, is_int);
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66 endfunction
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67
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68 ## Test pure RED, GREEN, BLUE colors
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69 %!assert (rgb2ntsc ([1 0 0]), [.299 .596 .211])
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70 %!assert (rgb2ntsc ([0 1 0]), [.587 -.274 -.523])
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71 %!assert (rgb2ntsc ([0 0 1]), [.114 -.322 .312])
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72
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73 %!test
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74 %! rgb_map = rand (64, 3);
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75 %! assert (ntsc2rgb (rgb2ntsc (rgb_map)), rgb_map, 1e-3);
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76
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77 %!test
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78 %! rgb_img = rand (64, 64, 3);
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79 %! assert (ntsc2rgb (rgb2ntsc (rgb_img)), rgb_img, 1e-3);
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80
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81 ## Test input validation
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82 %!error rgb2ntsc ()
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83 %!error rgb2ntsc (1,2)
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84 %!error <invalid data type 'cell'> rgb2ntsc ({1})
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85 %!error <RGB must be a colormap or RGB image> rgb2ntsc (ones (2,2))
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86
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87 ## Test ND input
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88 %!test
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89 %! rgb = rand (16, 16, 3, 5);
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90 %! yiq = zeros (size (rgb));
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91 %! for i = 1:5
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92 %! yiq(:,:,:,i) = rgb2ntsc (rgb(:,:,:,i));
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93 %! endfor
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94 %! assert (rgb2ntsc (rgb), yiq)