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AC N - Auto Correlation - Normalized

(09/10/96)

PURPOSE

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

  1. On completion of this operation, the output file will contain the auto-correlation function. The origin is at: (NSAM/2 + 1, NROW/2 + 1).

  2. The input data must be real.

  3. 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).

SUBROUTINES

ACRS_2, ACRS_2R, ACRS_3, ACRS_3R

CALLER

CORR1

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