1######################################################################## 2## 3## Copyright (C) 1999-2021 The Octave Project Developers 4## 5## See the file COPYRIGHT.md in the top-level directory of this 6## distribution or <https://octave.org/copyright/>. 7## 8## This file is part of Octave. 9## 10## Octave is free software: you can redistribute it and/or modify it 11## under the terms of the GNU General Public License as published by 12## the Free Software Foundation, either version 3 of the License, or 13## (at your option) any later version. 14## 15## Octave is distributed in the hope that it will be useful, but 16## WITHOUT ANY WARRANTY; without even the implied warranty of 17## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18## GNU General Public License for more details. 19## 20## You should have received a copy of the GNU General Public License 21## along with Octave; see the file COPYING. If not, see 22## <https://www.gnu.org/licenses/>. 23## 24######################################################################## 25 26## -*- texinfo -*- 27## @deftypefn {} {@var{hsv_map} =} rgb2hsv (@var{rgb_map}) 28## @deftypefnx {} {@var{hsv_img} =} rgb2hsv (@var{rgb_img}) 29## Transform a colormap or image from RGB to HSV color space. 30## 31## A color in the RGB space consists of red, green, and blue intensities. 32## 33## A color in HSV space is represented by hue, saturation and value 34## (brightness) levels in a cylindrical coordinate system. Hue is the 35## azimuth and describes the dominant color. Saturation is the radial 36## distance and gives the amount of hue mixed into the color. Value is 37## the height and is the amount of light in the color. 38## 39## Output class and size will be the same as input. 40## 41## @seealso{hsv2rgb, rgb2ind, rgb2gray} 42## @end deftypefn 43 44function hsv = rgb2hsv (rgb) 45 46 if (nargin != 1) 47 print_usage (); 48 endif 49 50 [rgb, sz, is_im, is_nd] ... 51 = colorspace_conversion_input_check ("rgb2hsv", "RGB", rgb); 52 53 ## get the max and min for each row 54 s = min (rgb, [], 2); 55 v = max (rgb, [], 2); 56 57 ## set hue to zero for undefined values (gray has no hue) 58 h = zeros (rows (rgb), 1); 59 notgray = (s != v); 60 61 ## blue hue 62 idx = (v == rgb(:,3) & notgray); 63 if (any (idx)) 64 h(idx) = 2/3 + 1/6 * (rgb(idx,1) - rgb(idx,2)) ./ (v(idx) - s(idx)); 65 endif 66 67 ## green hue 68 idx = (v == rgb(:,2) & notgray); 69 if (any (idx)) 70 h(idx) = 1/3 + 1/6 * (rgb(idx,3) - rgb(idx,1)) ./ (v(idx) - s(idx)); 71 endif 72 73 ## red hue 74 idx = (v == rgb(:,1) & notgray); 75 if (any (idx)) 76 h(idx) = 1/6 * (rgb(idx,2) - rgb(idx,3)) ./ (v(idx) - s(idx)); 77 endif 78 h(h < 0) += 1; # correct for negative red 79 80 ## set the saturation 81 s(! notgray) = 0; 82 s(notgray) = 1 - s(notgray) ./ v(notgray); 83 84 hsv = [h, s, v]; 85 hsv = colorspace_conversion_revert (hsv, sz, is_im, is_nd); 86 87endfunction 88 89 90## Test pure colors and gray 91%!assert (rgb2hsv ([1 0 0]), [0 1 1]) 92%!assert (rgb2hsv ([0 1 0]), [1/3 1 1]) 93%!assert (rgb2hsv ([0 0 1]), [2/3 1 1]) 94%!assert (rgb2hsv ([1 1 0]), [1/6 1 1]) 95%!assert (rgb2hsv ([0 1 1]), [1/2 1 1]) 96%!assert (rgb2hsv ([1 0 1]), [5/6 1 1]) 97%!assert (rgb2hsv ([0.5 0.5 0.5]), [0 0 0.5]) 98 99## Test tolarant input checking on floats 100%!assert (rgb2hsv ([1.5 1 1]), [0 1/3 1.5], eps) 101 102%!test 103%! rgb_map = rand (64, 3); 104%! assert (hsv2rgb (rgb2hsv (rgb_map)), rgb_map, 1e-6); 105 106%!test 107%! rgb_img = rand (64, 64, 3); 108%! assert (hsv2rgb (rgb2hsv (rgb_img)), rgb_img, 1e-6); 109 110## support sparse input 111%!assert (rgb2hsv (sparse ([0 0 1])), sparse ([2/3 1 1])) 112%!assert (rgb2hsv (sparse ([0 1 1])), sparse ([1/2 1 1])) 113%!assert (rgb2hsv (sparse ([1 1 1])), sparse ([0 0 1])) 114 115## Test input validation 116%!error rgb2hsv () 117%!error rgb2hsv (1,2) 118%!error <invalid data type 'cell'> rgb2hsv ({1}) 119%!error <RGB must be a colormap or RGB image> rgb2hsv (ones (2,2)) 120 121## Test ND input 122%!test 123%! rgb = rand (16, 16, 3, 5); 124%! hsv = zeros (size (rgb)); 125%! for i = 1:5 126%! hsv(:,:,:,i) = rgb2hsv (rgb(:,:,:,i)); 127%! endfor 128%! assert (rgb2hsv (rgb), hsv); 129 130## Test output class and size for input images. 131## Most of the tests only test for colormap input. 132 133%!test 134%! hsv = rgb2hsv (rand (10, 10, 3)); 135%! assert (class (hsv), "double"); 136%! assert (size (hsv), [10 10 3]); 137 138%!test 139%! hsv = rgb2hsv (rand (10, 10, 3, "single")); 140%! assert (class (hsv), "single"); 141%! assert (size (hsv), [10 10 3]); 142 143%!test 144%! rgb = (rand (10, 10, 3) * 3 ) - 0.5; # values outside range [0 1] 145%! hsv = rgb2hsv (rgb); 146%! assert (class (hsv), "double"); 147%! assert (size (hsv), [10 10 3]); 148 149%!test 150%! rgb = (rand (10, 10, 3, "single") * 3 ) - 0.5; # values outside range [0 1] 151%! hsv = rgb2hsv (rgb); 152%! assert (class (hsv), "single"); 153%! assert (size (hsv), [10 10 3]); 154 155%!test 156%! hsv = rgb2hsv (randi ([0 255], 10, 10, 3, "uint8")); 157%! assert (class (hsv), "double"); 158%! assert (size (hsv), [10 10 3]); 159 160%!test 161%! hsv = rgb2hsv (randi ([0 65535], 10, 10, 3, "uint16")); 162%! assert (class (hsv), "double"); 163%! assert (size (hsv), [10 10 3]); 164 165%!test 166%! hsv = rgb2hsv (randi ([-128 127], 10, 10, 3, "int8")); 167%! assert (class (hsv), "double"); 168%! assert (size (hsv), [10 10 3]); 169 170%!test 171%! rgb_double = reshape ([1 0 1 .5 1 1 0 .5 0 1 1 .5], [2 2 3]); 172%! rgb_uint8 = reshape (uint8 ([255 0 255 128 255 255 0 128 0 255 255 128]), 173%! [2 2 3]); 174%! rgb_int16 = int16 (double (rgb_double * uint16 (65535)) -32768); 175%! expected = reshape ([1/6 1/2 5/6 0 1 1 1 0 1 1 1 .5], [2 2 3]); 176%! 177%! assert (rgb2hsv (rgb_double), expected); 178%! assert (rgb2hsv (rgb_uint8), expected, 0.005); 179%! assert (rgb2hsv (single (rgb_double)), single (expected)); 180