Computes the normalized auto-correlation function of a picture
by using the Fourier transform relationship. The dimension
of the picture need not be a power of two (see "FT" for
restrictions). Works for 2D and 3D.
SEE ALSO
AC [Auto Correlation] AC MS [Auto Correlation - MaSked and normalized] CC [Cross Correlation] CC N [Cross Correlation - Normalized] CN [CoNvolution] CN N [CoNvolution - Normalized] FT [Fourier Transform]
USAGE
.OPERATION: AC N
.INPUT FILE: PIC001
[Enter the name of the picture to be auto-correlated.]
.OUTPUT FILE: ACF001
[Enter name of the file which will contain the auto-correlation
coefficients.]
NOTES
On completion of this operation, the output file will contain
the auto-correlation function. The origin is at:
(NSAM/2 + 1, NROW/2 + 1).
The input data must be real.
If the data cannot fit into the memory, use the 'FT' and 'MU'
commands to calculate the ACF:
FT
INPUT
FOUR
SQ
FOUR
MODFT
FT
MODFT
ACF
WARNING: The orgin of the ACF calculated in
this way is in (1,1).