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AC - Auto Correlation

(09/10/96)

PURPOSE

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

  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). The ACF is not normalized.

  2. The type of input data can be either real or Fourier.

  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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