do j = 1 to hbound(image,1);
   do i = 0 to hbound(image,2);
      color = image(i,j);
      R = substr(color, 17, 8);
      G = substr(color, 9, 8);
      B = substr(color, 1, 8);
      grey =  trunc(0.2126*R + 0.7152*G + 0.0722*B);
      greybits = grey;
      image(i,j) = substr(greybits, length(greybits)-7, 8);
   end;
end;