tion.

 <p> The method is also supplied with five scratch arrays.
 These arrays may be used within the method for any purpose.
 At method exit, the array at the index given by the return
 value of the method should contain the filtered data.  The
 return value will also be used as the filter type.

 <p> The default implementation of the method performs a trial
 encoding with each of the filter types, and computes the sum of
 absolute values of the differences between the raw bytes of the
 current row and th