Mercurial > octave
view scripts/image/ntsc2rgb.m @ 20657:bc51aa0d604a
ntsc2rgb.m: add more tests for scaling and truncation of values outside [0 1].
author | Carnë Draug <carandraug@octave.org> |
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date | Sun, 25 Oct 2015 19:34:56 +0000 |
parents | 175aed5acb85 |
children | eafc22e4c857 |
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## Copyright (C) 1994-2015 John W. Eaton ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 3 of the License, or (at ## your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {Function File} {@var{rgb_map} =} ntsc2rgb (@var{yiq_map}) ## @deftypefnx {Function File} {@var{rgb_img} =} ntsc2rgb (@var{yiq_img}) ## Transform a colormap or image from luminance-chrominance (NTSC) space to ## red-green-blue (RGB) color space. ## ## Implementation Note: ## The conversion matrix is chosen to be the inverse of the matrix used for ## rgb2ntsc such that ## ## @example ## x == ntsc2rgb (rgb2ntsc (x)) ## @end example ## ## @sc{matlab} uses a slightly different matrix where rounding means the ## equality above does not hold. ## @seealso{rgb2ntsc, hsv2rgb, ind2rgb} ## @end deftypefn ## Author: Tony Richardson <arichard@stark.cc.oh.us> ## Created: July 1994 ## Adapted-By: jwe function rgb = ntsc2rgb (yiq) if (nargin != 1) print_usage (); endif [yiq, cls, sz, is_im, is_nd, is_int] ... = colorspace_conversion_input_check ("ntsc2rgb", "YIQ", yiq); ## Conversion matrix constructed from 'inv (rgb2ntsc matrix)'. ## See programming notes in rgb2ntsc.m. Note: Matlab matrix for inverse ## is slightly different. We prefer this matrix so that ## x == ntsc2rgb (rgb2ntsc (x)) rather than maintaining strict compatibility ## with Matlab. trans = [ 1.0, 1.0, 1.0; 0.95617, -0.27269, -1.10374; 0.62143, -0.64681, 1.70062 ]; rgb = yiq * trans; ## truncating / scaling of double rgb values for Matlab compatibility ## (Other input types are not supported by Matlab. We deal with ## them anyways, but do not truncate or scale those.) if (cls == "double") rgb = max (0,rgb); idx = find (any (rgb'>1)); rgb(idx,:) = rgb(idx,:) ./ (max (rgb(idx,:), [], 2) * ones (1,3)); endif rgb = colorspace_conversion_revert (rgb, cls, sz, is_im, is_nd, is_int); endfunction %!shared trans %! trans = [ 1.0, 1.0, 1.0; %! 0.95617, -0.27269, -1.10374; %! 0.62143, -0.64681, 1.70062 ]; ## Test pure R, G, B colors %!assert (ntsc2rgb ([.299 .596 .211]), [1 0 0], 1e-5) %!assert (ntsc2rgb ([.587 -.274 -.523]), [0 1 0], 1e-5) %!assert (ntsc2rgb ([.114 -.322 .312]), [0 0 1], 1e-5) %!test %! rgb_map = rand (64, 3); %! assert (ntsc2rgb (rgb2ntsc (rgb_map)), rgb_map, 1e-3); %!test %! rgb_img = rand (64, 64, 3); %! assert (ntsc2rgb (rgb2ntsc (rgb_img)), rgb_img, 1e-3); ## test cropping of rgb output %!assert (ntsc2rgb ([1.5 0 0]), [1 1 1]); ## Test scaling of output. After conversion, cut of negative values ## and scaling of all the others relative to the maximum above 1. %!test %! ntsc = [0.4229 0.0336 0.7184]; %! rgb = ntsc * trans; # [0.9014 -0.0509 1.6075] %! rgb(1) /= rgb(3); # scaled based on the maximum %! rgb(2) = 0; # cut to 0 %! rgb(3) = 1; # cut to 1 %! assert (ntsc2rgb (ntsc), rgb) ## test scaling when conversion has more than one value above 1 ## (check that it does pick the maximum) %!test %! ntsc = [0.8229 0.3336 0.7184]; %! rgb = ntsc * trans; # [1.58831 0.26726 1.67642] %! rgb /= rgb(3); %! assert (ntsc2rgb (ntsc), rgb) ## check scaling for more than 1 row %!test %! ntsc = [0.4229 0.0336 0.7184 %! 0.8229 0.3336 0.7184]; %! rgb = ntsc * trans; # [0.9014 -0.0509 1.6075; 1.58831 0.26726 1.67642] %! rgb(1,1) /= rgb(1,3); %! rgb(1,2) = 0; %! rgb(1,3) = 1; %! rgb(2,:) /= rgb(2,3); %! assert (ntsc2rgb (ntsc), rgb) ## Test input validation %!error ntsc2rgb () %!error ntsc2rgb (1,2) %!error <YIQ must be a colormap or YIQ image> ntsc2rgb (uint8 (1)) %!error <YIQ must be a colormap or YIQ image> ntsc2rgb (ones (2,2)) ## Test ND input %!test %! yiq = rand (16, 16, 3, 5); %! rgb = zeros (size (yiq)); %! for i = 1:5 %! rgb(:,:,:,i) = ntsc2rgb (yiq(:,:,:,i)); %! endfor %! assert (ntsc2rgb (yiq), rgb)