FFTUtilities: FFT Utilities

In mlpeck/zernike: Zernike Polynomials

FFT Utilities

Description

Miscellaneous utilities for working with 2D images in the Fourier domain.

Usage

wftophase(X, lambda=1)
padmatrix(X, npad, fill = mean(X, na.rm=TRUE))
submatrix(X, size = 255)
fftshift(X)
.up2(nr, nc=nr)

Arguments

X	A matrix
lambda	Value of the wavelength, in the same units as X
npad	Size of padded matrix
fill	Values to be assigned to padded matrix elements
size	Size of returned matrix
nr	A number
nc	A number

Details

wftophase computes the complex phase from wavefront values.

padmatrix pads a matrix to size npad x npad, placing the original matrix in the lower left hand corner of the padded matrix.

submatrix extracts a size x size matrix from the center of a larger matrix.

fftshift shuffles the quadrants of a matrix around to put the DC element (1,1) in the center of the transformed matrix, with spatial frequencies increasing to the right and up.

Value

A matrix transformation of the input matrix X.

.up2 returns the next higher power of 2 than max(nr, nc).

Note

These low level routines are used by several higher level functions that operate in the Fourier domain.

Author(s)

M.L. Peck [e-mail]

See Also

startest, fftfit.

mlpeck/zernike documentation built on March 28, 2024, 5:14 p.m.