update packages

[CreaPhase.git] / octave_packages / m / image / rgb2ntsc.m

diff --git a/octave_packages/m/image/rgb2ntsc.m b/octave_packages/m/image/rgb2ntsc.m
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+## Copyright (C) 1994-2012 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} {} rgb2ntsc (@var{rgb})
+## Transform a colormap or image from RGB to NTSC.
+## @seealso{ntsc2rgb}
+## @end deftypefn
+
+## Author: Tony Richardson <arichard@stark.cc.oh.us>
+## Created: July 1994
+## Adapted-By: jwe
+
+function yiq = rgb2ntsc (rgb)
+
+  if (nargin != 1)
+    print_usage ();
+  endif
+
+  ## If we have an image convert it into a color map.
+  if (ismatrix (rgb) && ndims (rgb) == 3)
+    is_image = true;
+    Sz = size (rgb);
+    rgb = [rgb(:,:,1)(:), rgb(:,:,2)(:), rgb(:,:,3)(:)];
+    ## Convert to a double image.
+    if (isinteger (rgb))
+      C = class (rgb);
+      low = double (intmin (C));
+      high = double (intmax (C));
+      rgb = (double (rgb) - low) / (high - low);
+    endif
+  else
+    is_image = false;
+  endif
+
+  if (! ismatrix (rgb) || columns (rgb) != 3)
+    error ("rgb2ntsc: argument must be a matrix of size Nx3 or NxMx3");
+  endif
+
+  ## Convert data
+  trans = [ 0.299,  0.596,  0.211;
+            0.587, -0.274, -0.523;
+            0.114, -0.322,  0.312 ];
+
+  yiq = rgb * trans;
+
+  ## If input was an image, convert it back into one.
+  if (is_image)
+    yiq = reshape (yiq, Sz);
+  endif
+
+endfunction