Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / image-1.0.15 / rgb2gray.m

diff --git a/octave_packages/image-1.0.15/rgb2gray.m b/octave_packages/image-1.0.15/rgb2gray.m
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+## Copyright (C) 2000, 2001  Kai Habel
+##
+## This program 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 2 of the License, or
+## (at your option) any later version.
+##
+## This program 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 this program; If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} @var{gray}= rgb2gray (@var{rgb})
+## Converts an RGB image to a gray scale image, or a color map
+## to a gray map.
+##
+## If the input is an RGB image, the conversion to a gray image
+## is computed as the mean value of the color channels.
+##
+## If the input is a color map it is converted into the YIQ space
+## of ntsc. The luminance value (Y) is taken to create a gray color map.
+## R = G = B = Y
+## @end deftypefn
+
+## Author:     Kai Habel <kai.habel@gmx.de>
+## Date:       19. March 2000
+
+function gray = rgb2gray (rgb)
+
+  if (nargin != 1)
+    print_usage();
+  endif
+
+  if (ismatrix (rgb) && ndims(rgb) == 2 && columns(rgb) == 3)
+    ntscmap = rgb2ntsc (rgb);
+    gray = ntscmap (:, 1) * ones (1, 3);
+  elseif (ismatrix(rgb) && ndims(rgb) == 3)
+    switch(class(rgb))
+    case "double"
+      gray = mean(rgb,3);
+    case "uint8"
+      gray = uint8(mean(rgb,3));
+    case "uint16"
+      gray = uint16(mean(rgb,3));
+    otherwise
+      error("rgb2gray: unsupported class %s", class(rgb));
+    endswitch
+  else
+    error("rgb2gray: the input must either be an RGB image or a color map");
+  endif
+endfunction