Computes the 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 N [Auto Correlation - Normalized] AC MS [Auto Correlation - MaSked and normalized] CC [Cross Correlation] CC N [Cross Correlation - Normalized] CN [CoNvolution] CN N [CoNvolution - Normalized]
USAGE
.OPERATION: AC
.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 ACF is not normalized.
The type of input data can be either real or Fourier.
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).