Help for IFFT

PURPOSE:
"ifft" allows the user to interactively and selectively modify areas of an FFT.

EXECUTION:

Example

	TAE> ifft inp=scr:fft out=(scr:tmpfil,scr:newfft)

	(Parameters are allowable in the command line.)

	REFORMATTING INPUT

	(A couple minutes will elapse, then the FFT will be drawn on the
	allocated display device.)

	IFFT READY
	Enter Parameters:  

	(The program is now waiting for one of two types of input.
	    The first type of input is one of the normal commands. 
	Commands are available to set the shape and dimensions of
	the area to be modifed (CIRCLE, RECTANGL, VERTEX mode), to move
	the cursor (PCURS, WCURS), read the DN value and position of the
	cursor (RCURS), or adjust the display (SLDS, SSDS, U, D, L, R).
	The user can also display the phase picture ('PHASE) rather than
	the default amplitude picture ('AMPLITUD), or can specify that 
	points outside of the defined area ('EXTERIOR) are to be changed
	rather the points inside (reset by 'INTERIOR).  Finally, points
	within the defined area can be multiplied by a factor (MULTIPLY)
	and/or increased or decreased by a constant (ADD).
	    The second type of input is a simple RETURN, which tells the
	program to go ahead and accept an area definition from the
	trackball and perform the modification.  
	    The default modification area is a circle, 10 pixels in
	radius; points inside are multiplied by 0.10.  Whenever the
	modification function is changed, the program will print out
	the complete status; e.g., if you use the ADD command immediately
	after entering the program, IFFT will show that 'INTERIOR, CIRCLE=10,
	and MULT=0.10 are in effect.)

	Enter Parameters:  CIRCLE=20 MULT=0.0 ADD=45

	TRANSFORM MODIFICATION IN EFFECT:
	CIRCLE   20        INTERIOR   MULT   0.00

	Enter Parameters:  (Press RETURN to define area)
	
	POSITION THE CURSOR AND PRESS <CR>

	(Position the cursor using the trackball and press <CR>.
	The program will draw a circle around the specified
	point and come back with ...)

	OK ?   HIT <CR> IF OK OR TYPE NO TO REDO
	Enter Parameters:  (Press RETURN)

	("ifft" will perform the mod and return)

	Enter Parameters:'EXIT

	WRITING OUTPUT
	
	(Several minutes will elapse during output)

	TAE>

OPERATION:

Sequence of steps:

1.  Process command line parameters (MAIN44)
2.  Copy input FFT into temporary dataset (DSRN 1), reformatting the data
    so that DC is moved from the upper-left corner to the center (FFT_FORMAT).
3.  Display the FFT (DISPLY)
4.  Get parameters from user and process as appropriate (KEYWRD).
    If none, goto step 9.
5.  If the display needs to be refreshed (e.g., user changed display format
    using SS, SSDS, et al.) redisplay screen (DISPLY).
6.  If user changed modification area shape, size, or handling, print current
    status.
7.  If cursor position is to be read or changed, do it (CURSOR).
8.  If done, copy temporary file into output file, moving DC back to the
    upper-left corner, and exit the program.  Otherwise, goto step 4.
9.  Modify mode (MODIFY): 
    a.  Get trackball location
    b.  If circle or rectangle, draw shape at current location and goto d.
    c.  If vertex mode, see if first point.  If so, get next at a.
        If middle point and not same as the last, draw segment to last
        point and get next point at a.  (3000 points are allowed.)
        If same point as last time, complete polygon.
    d.  Prompt user to accept or reject area.  If rejected, goto step 4.
        Otherwise, perform current modifications on area and goto 4.

NOTE: Initialization of displays via the VRDI XDGLINIT function sometimes
does not work on the Unix platforms.  This was per discussions with Bob
Deen and E. Cruz on 30 May 1994.  Should the display not appear correct,
the following two work arounds were suggested: 1) Click on the display
screen, or 2) restart the display.  Usually item 1 will cause the display
to be reinitialized properly.

WRITTEN BY:  John Reimer, May 1983
COGNIZANT PROGRAMMER:  John Reimer
REVISION:  New
REVISION:  Made portable for UNIX ... V. Unruh ... (CRI) (May  8, 1995)
22-04-98....RRP  Removed constant IMP from call to XDIFILL and replaced
                 with GRAPHICSPLANE variable which gets its value from
                 XDSGRAPH subroutine.
16-07-98....RRP  Added INTEGER XDSGRAPH to implie that the function returns
                 a integer value and not a float (AR-100438).