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view scripts/image/rgb2gray.m @ 30564:796f54d4ddbf stable
update Octave Project Developers copyright for the new year
In files that have the "Octave Project Developers" copyright notice,
update for 2021.
In all .txi and .texi files except gpl.txi and gpl.texi in the
doc/liboctave and doc/interpreter directories, change the copyright
to "Octave Project Developers", the same as used for other source
files. Update copyright notices for 2022 (not done since 2019). For
gpl.txi and gpl.texi, change the copyright notice to be "Free Software
Foundation, Inc." and leave the date at 2007 only because this file
only contains the text of the GPL, not anything created by the Octave
Project Developers.
Add Paul Thomas to contributors.in.
author | John W. Eaton <jwe@octave.org> |
---|---|
date | Tue, 28 Dec 2021 18:22:40 -0500 |
parents | 7854d5752dd2 |
children |
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######################################################################## ## ## Copyright (C) 2018-2022 The Octave Project Developers ## ## See the file COPYRIGHT.md in the top-level directory of this ## distribution or <https://octave.org/copyright/>. ## ## 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 ## <https://www.gnu.org/licenses/>. ## ######################################################################## ## -*- texinfo -*- ## @deftypefn {} {@var{I} =} rgb2gray (@var{rgb_img}) ## @deftypefnx {} {@var{gray_map} =} rgb2gray (@var{rgb_map}) ## Transform an image or colormap from red-green-blue (RGB) color space to ## a grayscale intensity image. ## ## The input may be of class uint8, int8, uint16, int16, single, or double. ## The output is of the same class as the input. ## ## Implementation Note: ## The grayscale intensity is calculated as ## ## @example ## @group ## @var{I} = 0.298936*@var{R} + 0.587043*@var{G} + 0.114021*@var{B} ## @end group ## @end example ## ## @noindent ## which corresponds to the luminance channel when RGB is translated to ## @nospell{YIQ} as documented in @url{https://en.wikipedia.org/wiki/YIQ}. ## @seealso{rgb2hsv, rgb2ind} ## @end deftypefn function I = rgb2gray (rgb) if (nargin < 1) print_usage (); endif is_int = isinteger (rgb); if (is_int) cls = class (rgb); endif [rgb, sz, is_im, is_nd] ... = colorspace_conversion_input_check ("rgb2gray", "RGB", rgb); ## Reference matrix for transform from http://en.wikipedia.org/wiki/YIQ. ## Matlab uses this matrix for their conversion with oddly more precision. xform = [0.298936; 0.587043; 0.114021]; I = rgb * xform; sz(3) = 1; # grayscale images have 3rd dimension of length 1 I = colorspace_conversion_revert (I, sz, is_im, is_nd); ## Restore integer class if necessary if (is_int) if (cls(end) == "8") # uint8 or int8 I *= 255; if (cls(1) == "i") # int8 I -= 128; endif else # uint16 or int16 I *= 65535; if (cls(1) == "i") # int16 I -= 32768; endif endif I = feval (cls, I); endif endfunction ## Test pure RED, GREEN, BLUE colors %!assert (rgb2gray ([1 0 0]), 0.298936) %!assert (rgb2gray ([0 1 0]), 0.587043) %!assert (rgb2gray ([0 0 1]), 0.114021) ## test tolerance input checking on floats %! assert (rgb2gray ([1.5 1 1]), 1.149468, -1.6e-3); ## Test ND input %!test %! rgb = rand (16, 16, 3, 5); %! I = zeros (16, 16, 1, 5); %! for i = 1:5 %! I(:,:,1,i) = rgb2gray (rgb(:,:,:,i)); %! endfor %! assert (rgb2gray (rgb), I); ## Test output class and size for input images. ## Most of the tests only test for colormap input. %!test %! I = rgb2gray (rand (10, 10, 3)); %! assert (class (I), "double"); %! assert (size (I), [10 10]); %!test %! I = rgb2gray (rand (10, 10, 3, "single")); %! assert (class (I), "single"); %! assert (size (I), [10 10]); %!test %! rgb = (rand (10, 10, 3) * 3 ) - 0.5; # values outside range [0 1] %! I = rgb2gray (rgb); %! assert (class (I), "double"); %! assert (size (I), [10 10]); %!test %! rgb = (rand (10, 10, 3, "single") * 3 ) - 0.5; # values outside range [0 1] %! I = rgb2gray (rgb); %! assert (class (I), "single"); %! assert (size (I), [10 10]); %!test %! I = rgb2gray (randi ([0 255], 10, 10, 3, "uint8")); %! assert (class (I), "uint8"); %! assert (size (I), [10 10]); %!test %! I = rgb2gray (randi ([0 65535], 10, 10, 3, "uint16")); %! assert (class (I), "uint16"); %! assert (size (I), [10 10]); %!test %! I = rgb2gray (randi ([-128 127], 10, 10, 3, "int8")); %! assert (class (I), "int8"); %! assert (size (I), [10 10]); %!test %! I = rgb2gray (randi ([-32768 32767], 10, 10, 3, "int16")); %! assert (class (I), "int16"); %! assert (size (I), [10 10]); %!test %! rgb_double = reshape ([1 0 0 0 0 1 0 0 0 0 1 0], [2 2 3]); %! rgb_uint8 = reshape (uint8 ([255 0 0 0 0 255 0 0 0 0 255 0]), %! [2 2 3]); %! rgb_int16 = int16 (double (rgb_double * uint16 (65535)) - 32768); %! expected = [0.298936, 0.114021; 0.587043, 0.0]; %! %! assert (rgb2gray (rgb_double), expected); %! assert (rgb2gray (rgb_uint8), uint8 (expected*255)); %! assert (rgb2gray (single (rgb_double)), single (expected)); ## Test input validation %!error <Invalid call> rgb2gray () %!error <invalid data type 'cell'> rgb2gray ({1}) %!error <RGB must be a colormap or RGB image> rgb2gray (ones (2,2))