Level 2 Help for FFTFIT

INP specifies the complex Fourier transform and the image picture used to 
modify the transform, in that order.  The Fourier transform must have been
created by "fft2" or "fft22".

OUT specifies the name of the modified Fourier transform.

MODE=MULT (or 'MULT) selects the multiplication mode of "fftfit".  The
default is the amplitude matching mode. 

LINE specifies the line number in the input image which corresponds to 
line one (the DC line) in FT.  The default is NL/2+1 where NL is the 
number of lines in FT.

SAMPLE specifies the sample number in the input image which corresponds with
column one (the DC column) in FT.  The default is NPIX/2+1 where NPIX is
one eighth the number of samples in FT.

'FIND will compute the LINE and SAMPLE parameter values from the input image by
locating the position of the largest DN value.  If more than one pixel has the
maximum DN value, the centroid of all maximum DN values is selected. Default is
to the LINE, SAMPLE defaults. 

SCALE specifies the scaling factor applied to the input image before
processing. 
    In the multiplicative mode, SCALE (by default) equals one divided by the
mean DN value measured within the sampling area specified by the SET keyword or
its defaults; in the matching mode, where FTOUT is made proportional to the
input picture, SCALE equals A-bar divided by the mean DN value, where A-bar is
a similarly-determined reference amplitude in FT. 
    The SCALE keyword allows the user to bypass all of these calculations and
explicitly specify the scaling factor to be used.  All other parameters in this
example are allowed to default. 

SET directs the program to calculate the scaling value SCALE from an area
defined by the integer values, 3 and 5 in this example, in both PIX and FT.
A-bar is obtained from the mean amplitude in the shaded area bounded by 
N3 and N4 in the upper left quadrant to FT (see figure).

		N3	N4		NPIX=NS/8
	+-------+-------+----------------------- 	|DC	|///////|			|DC
	|	|///////|			|
      N3+-------+///////|			|
	|///////////////|			|	matrix of 
	|///////////////|			|	complex FFT values
      N4+---------------+			|
	|					|
	|					|
	|					|
	|					|
	|					|
      NL+---------------------------------------          DC					 DC

The mean DC value is computed from the corresponding area in PIX starting at 
(LINE,SAMPLE) rather than at (1,1) as in FT.  Default is SET=(2,3).