Calculates the autocorrelation function of the current ROI. At present this must be a power of two pixels in length for both of the two dimensions. The circular autocorrelation function is calculated. To calculate a non-circular autocorrelation, first place the region in a larger region of zero valued pixels. At least 2n-1 elements are necessary to completely avoid any wrap-around.
The prompt:
CENTRE OUTPUT [YES]:
appears. If the default "YES" is accepted, then the zero "frequency" will be centred in the output, otherwise the zero "frequency" correlation will be the first pixel.