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+## Copyright (C) 2011 Santiago Reyes González
+##
+## 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.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} @var{B} =  rgb2ycbcr(@var{A})
+## Perform colour convertion on a given image.
+## The image @var{A} must be a image.
+## The convertion change the image RGB to YCbCr, i.e.
+## @example
+## imOut = rgb2ycbcr(imIn);
+## @end example
+## @seealso{cmunique, cmpermute}
+## @end deftypefn
+
+function im_out =  rgb2ycbcr(im)
+  dimensiones=size(im);
+  if (length(dimensiones) == 3)
+    row=dimensiones(1,1);
+    column=dimensiones(1,2);
+    depth=dimensiones(1,3);
+  end
+  if (depth == 3)
+    im_cal = im2double(im);
+    for i=1:row
+      for j=1:column
+        im_out(i,j,1) = uint8(floor(77*im_cal(i,j,1)+ 150*im_cal(i,j,2) + 29*im_cal(i,j,3)));
+        im_out(i,j,2) = uint8(floor(((-44*im_cal(i,j,1) - 87*im_cal(i,j,2) + 131*im_cal(i,j,3))/256 + 0.5)*256));
+        im_out(i,j,3) = uint8(floor(((131*im_cal(i,j,1) - 110*im_cal(i,j,2) - 21*im_cal(i,j,3))/256 + 0.5)*256));
+      endfor
+    endfor
+  else
+    error ("rgb2ycbcr: the matrix mmust be a NxMx3");
+  endif
+endfunction