====== RGB2GS - RGB to gray scale ======
  * Convert RGB image to gray scale image.
  * <m>f = 0.299R+0.587G+0.114B</m>
<code matlab>
% RGB to GrayScale
function [gs]=RGB2GS(rgb)

% GS = 0.299R+0.587G+0.114B
gs = 0.299*rgb(:,:,1)+0.587*rgb(:,:,2)+0.114*rgb(:,:,3);

return;

</code>