Level 2 Help for TFILT

 input file

 output file and one or two scratch files

 If the primary input is multi-band, then three output files are required
 of which the last two are scratch files.  Otherwise, only one scratch
 file is required, which is the second output file.

 The first output file is always the output image.

 (number of lines,number of samples,
 starting line number,starting sample number)
 Specifies area of input image to process.

Starting line.

Starting sample.

Number of lines.

Number of samples per line.

 NLW is an integer which specifies the number of lines dimension
 of the convolution window.

 The default is NLW=NL/10 where NL is the number of lines in the size field.
 If NLW is an even number (whether user-specified or default), then 1 is
 added to get an odd number.  E.g., for a 100x100 image, the default is
 NLW=11.

 NSW is an integer which specifies the number of pixels dimension of the
 convolutional window.  The default is NL/10.

 If NLW is an even number (whether user-specified or default), then 1 is
 added to get an odd number.  

 THRESH is an integer which specifies a threshold
 level above which pixels will be accepted into
 the average (low pass).  When a pixel lies 
 below THRESH the output picture pixel will
 always be zero.  The default is THRESH=0,
 which, at least for byte, converts tfilt into
 a linear boxfilter.

(NOTE:  until 20-Dec-2012, the default for THRESH was
-1 and the criterion for exclusion was DN<=THRESH.  This
was changed when support for REAL*4 data was added, to
make the behaviour at THRESH=0 consistent with integer
data types.  As a result, to obtain the same results as
the older version of THRESH, 1 must be added to the old
value.)

 This parameter specifies the type of filter to be used.
 
 HIGH: performs a high pass filter using the following equation:
 	OUT = (DN-AVGDN)*BOOST+DCTRAN*DN+DCLEVEL
 
 SCENE: performs a SCENE filter using the following equation:
	OUT = (DN-AVGDN)/ADVDN*SCALE+DCTRAN*DN+DCLEVEL
 
 LOW:  performs a low pass filter using the following equation:
	OUT = AVGDN*BOOST+OFFSET
 
 DIVIDE: performs a divide filter using the following equation:
	OUT = DN/AVGDN*SCALE+DCTRAN*DN+OFFSET
	 This is the default filter.

 SCALE is a real number, used to scale output for SCENE and
 DIVIDE filters only.  The default is 100.

 DCTRAN is a real, DC transmission. Default = 0.0  (See the section on 
 DCTRAN in the main help section for tfilt.)

 BOOST is a real number, used to scale output for HIGH and LOW
 filters only.   Default is 1.0

 DCLEVEL is a real additive factor in SCENE and HIGH filters only.
 Default is 128.0

 OFFSET is a real additive factor used with
 LOW and DIVIDE filters only. (Default = 0.5)