Help for FFTFLIP

PURPOSE:
"fftflip" accepts one FFT or a matrix of FFT outputs from programs "fft2",
or "fft22", and rearranges the internal structure of each FFT
such that DC is moved from the upper-left corner to center.  An optional
transposition can also be made along the diagonal (upper-left to lower-right).
"fftflip" differs from "fftpic" in that no automatic scaling of the FFT is
performed, and no beginning and trailing samples are added.

EXECUTION:

	fftflip INP OUT SIZE PARAMS

where:  INP  is the input FFT or matrix of FFTs.
	OUT  is the output file.
        SIZE specifies a subarea of the input file to process.
	PARAMS includes other parameters descibed below and in Tutor mode.
OPERATION:
"fftflip" performs the operation shown in the following diagrams.
The letters A,B,C,D refer to fft quadrants.
+-------+-------+     +-------+-------+     +-------+------- |DC     |       |     |       |       |     |       |       |
|       |       |     |       |       |     |       |       |
|   A   |   B   |     |   D   |   C   |     |   D'  |   B'  |
|       |       |     |       |       |     |       |       |
+-------+-------+ --> +-------+-------+ --> +-------+------- |       |       |     |       |DC     |     |       |DC     |
|       |       |     |       |       |     |       |       |
|   C   |   D   |     |   B   |   A   |     |   C'  |   A'  |
|       |       |     |       |       |     |       |       |
+-------+-------+     +-------+-------+     +-------+-------   INPUT FFT           DEFAULT OPERATION      WITH FLIP OPTION
                                            (' MEANS TRANSPOSE)

When the input is a matrix of FFTs, then the above operation is
performed on each FFT separately.

Obviously, there is nothing that compells the input to this program 
to be an FFT:  it will work on any arbitrary image;  however, the
operation described is most meaningful for an FFT, so that term is
used here.


LIMITATIONS
    (Removed Warning about slowness on VAX)

    Does not work with "COMP" images

EXAMPLES

	fftflip INP=A OUT=B NLW=32 LINE=0 'FLIP

	In this example, the FFT in file A will be rearranged and then the
	program will perform a transposition along the upper-left to lower-
	right diagonal.  The result will be written to file B.  NLW gives
	the FFT dimension in pixels; the default is 32.  LINE specifies the
	number of lines above and below DC which are to be averaged
	together as a form of pseudo apodizing; no averaging is desired in
	this case.  (If averaging were to be done, the DC parameter could
	also have been specified, which indicates the number of lines
	surrounding DC that are to be excluded from the averaging; the
	default is DC=1, that is, only the DC line is excluded.)

	insert INP=IN OUT=A (1,1,32,32)		(where 'IN' is image data)
	fft22 INP=A OUT=B POW=5 IFMT=BYTE OFMT=COMP
	cform INP=B OUT=A IN=COMP OUT=HALF SO=(9.76525,0.)
	fftflip INP=A OUT=B NLW=32 LINE=0 'FLIP
	f2 INP=B OUT=A 'HALF 'OUTH  	    FUNC="(32767./ALOG(32767.))*ALOG10(IN1)"
	linear INP=A OUT=B 'HALF 'OUTB STRE=(6000,14000) LIMI=(0,255)
	list B

	This example shows fftflip as used in a typical command sequence

WRITTEN BY:  J.J. Lorre,  23 January 1984

CONVERTED TO VAX BY:  A.S.Mazer, 11 May 1984


CURRENT COGNIZANT PROGRAMMER:  R. J. Bambery

    1984-05-11 A.S.Mazer - Converted to VAX 
    1985-08-01 L. W. Kamp - CONVERTED TO VICAR2, FIXED BUGS
    1994-09-05 A. Scop (CRI) - Made portable for UNIX 
    2012-12-19 R. J. Bambery - LINUX 64-bit changes, Internal format
                               is real, removed BYE,HALF limitation
    2016-06-08 W. L. Bunch - Migrated to MIPL