Name

acfp - calculate the autocorrelation function of an image using padding with zeroes and multiplication in Fourier space.

Usage

output = acfp(image, center=True)

Input

image
input image (real)
center
if set to True (default), the origin of the result is at the center; if set to False, the origin is at (0,0), the option is much faster, but the result is difficult to use

Output

output
autocorrelation function of the input image. Real. The origin of the autocorrelation function (term ccf(0,0,0)) is located at (int[n/2], int[n/2], int[n/2]) in 3D, (int[n/2], int[n/2]) in 2D, and at int[n/2] in 1D.

Method

next by calculating Fourier transform of the image, then the modulus squared in Fourier space as `|hat(f)|^2`, then the inverse Fourier transform, and finally the acfp is windowed out using the size of original images.

Reference

Pratt, W. K., 1992. Digital image processing. Wiley, New York.

Author / Maintainer

Pawel A. Penczek

Keywords

category 1
FUNDAMENTALS
category 2
FOURIER

Files

fundamentals.py

Maturity

stable
works for most people, has been tested; test cases/examples available.

Bugs

None. It is perfect.

acfp (last edited 2013-07-01 13:12:42 by localhost)