Level 2 Help for FFT11

A VICAR labelled image file.  In Inverse mode, this must be of COMPLEX
format.

The output file.  In Forward mode, this will be of COMPLEX format.

The standard size field defining the area of the input picture that is to
be processed: (SL, SS, NL, NS), or:
 (starting line, stating sample, number of lines, number of samples).

If SS-1+NS exceeds the number of samples of the input image, then the input
data will be extrapolated using a cosine function.  The extrapolation
algorithm is identical to that used in FFT1AP, but results may differ slightly
as the extrapolation is performed on REAL*4 data in FFT11, but is rounded
to the input data type in FFT1AP.

For an Inverse transform, SS must be 1 and NS must equal the input size.

Starting line of the area to be processed.  See SIZE.

Starting sample of the area to be processed.  See SIZE.

Number of lines in the area to be processed.  See SIZE.

Number of samples in the area to be processed.  See SIZE.

Indicates that the inverse Fourier Transformation is to be performed
on the input file.   Default: forward transform is performed.

This specifies the output image format in the Inverse mode.  It is ignored
in the Forward mode.