**PURPOSE**- Calculates self-correlation coefficients for an image under a circular mask. Coefficients are normalized. Image is padded with zeros. Works only for real images (not their Fourier transforms!). Example.

**SEE ALSO****AC**[Auto Correlation ||] **AC N**[Auto Correlation - Normalized ||] **AC S**[Self Correlation ||] **AC NS**[Self Correlation - Normalized ||]

**USAGE**- .OPERATION: AC MSS

- .INPUT FILE: PIC001

[Enter the name of the image to be self-correlated.].OUTPUT FILE: MAC001

[Enter name of the file which will contain SAC coefficients.].MASK RADIUS: 25

[Enter radius of the circular mask which will be centered at NX/2+1, NY/2+1].(F)ULL OR (H)ALF OUTPUT FILE: F

['F' results in a autocorrelation function file with dimensions 2*NX, 2*NY (useful for mask radius =>MAX(NX/4,NY/4).

'H' results in a selfcorrelation function file with dimensions NX,NY (enough if one is interested only in lower order SACF coefficients. or mask radius is small)]

**NOTES**

- See documentation on 'AC' for the location of the origin.
- For non-masked self-correlation function use 'AC S'.
- Implemented by Paul Penczek.

**SUBROUTINES**- MACF, MACF_P, FMRS_2, FMRS_1, FFTMCF, ACRS_2, ACRS_2S

**CALLER**- CORR1

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