Help for FILTER

PURPOSE:

FILTER is a VICAR applications program which performs two-dimensional
convolution filtering.  For each output sample, the program computes
a weighted average of a rectangular set of input pixels followed by
a linear transformation.  FILTER may be used to perform high-pass or 
low-pass filtering.

EXECUTION:

   The following is the execution statement format for FILTER:

             FILTER INP=PIX OUT=OPIX PARAMS

   where INP, OUT, and PARAMS are parameters discussed in their res-
pective parameter sections. 
OPERATION:

FILTER accepts as input a rectangular set of weights and calculates each
output point OUT(l,s) as follows:
             _                                                       _
            |  nlw nsw                                                |   /
 XXX(l,s) = | SUM SUM  IN[l-(nlw+1)/2 + i , s-(nsw+1)/2 + j] * W(i,j) |  / DIV
            |_ i=1 j=1                                               _| /
and
   OUT(l,s) = (GAIN * XXX(l,s)) + OFF
where
	IN       is the input file
	W        is the weight matrix
	nlw      is the number of lines in the weight matrix
	nsw      is the number of samples in the weight matrix
	OFF,GAIN are the SCALE parameters
	DIV      is the DIVIDE parameter
EXAMPLES:

1) FILTER IN OUT NLW=3 NSW=5 WEIGHTS=(0,-1,-2,-1,-2,10)
   The file will be filtered with the weight table shown below:
         0   -1   -2   -1   0
	-1   -2   10   -2   -1
	 0   -1   -2   -1   0
   The final linear transformation is
		FP(L,S) = IN(L,S) / 6
   where 6 is the default for the DIVIDE parameter, (i.e., the sum of the
   entries in the weight table).
2) FILTER IN OUT NLW=3 NSW=5 SCALE=(-30,1) DIVIDE=3 WEIGHTS=(0,-1,-2,-1,-2,10)
   This is the same as the example above except the final transformation is 
   given by:
		FP(L,S) = 1.0*(IN(L,S)/3.0) -30.0

3) FILTER IN OUT NLW=3 NSW=5 'UPPER DNMIN=15 WEIGHTS=(-2,5,4,3,-1,-5,20,3,1,1)
   These parameters generate the horizontally nonsymmetric weights shown
   below:
   	 -2   5   4   3   -1
	 -5  20   3   1    1
	 -2   5   4   3   -1
   and output will be computed as follows:  If the output is less
   than or equal to 15 DN, it is set to 15 DN.  
4) FILTER IN OUT NLW=3 NSW=3 'ALL WEIGHTS=(-1,0,0,0,0,0,0,0,1)
   These parmeters will produce a diagonal gradient picture using this weight
   matrix:  
  	-1   0   0
	 0   0   0
	 0   0   1

5) FILTER (IN,KERNAL) OUT
   In this case, the filter weights are provided in the second input file.

COGNIZANT PROGRAMMER:  Ron Alley