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PowerSpectrum

PowerSpectrum[img] returns the power spectrum of img.

PowerSpectrum[img, {n₁, n₂, ... }] returns the power spectrum of img calculated using non-overlapping blocks of size n₁

PowerSpectrum[img, {n₁, n₂, ... }, {d₁, d₂, ... }] uses offset d_i at level i in img.

PowerSpectrum uses one of several classic nonparametric spectrum estimation methods: "DFT", "Welch", and "BlackmanTukey".

The default method is Method → "DFT". The power spectrum is effectively | DFT[img] |².

Welch's method returns a power spectrum of dimensions n₁

n₂ that is an average of the power spectra evaluated over blocks of dimensions n₁

n₂ that tile img. In each block the DFT method is used to compute the spectrum. Additionally, the samples of img may be windowed using any available window sequence.

The method by Blackman and Tukey calculates the power spectrum from the autocorrelation coefficients of img. The autocorrelation coefficients may be windowed using any available window sequence.

The desired window sequence is selected using option WindowType. The default window sequence is WindowsType → "Bartlett" (or equivalently "Triangular"). Other available window sequences are: "Rectangular", "Hamming", and "Blackman".

The argument img may be an array or a grayscale ImageData object.

See also User's Guide 8.3.

New in Version 2.

Examples

This loads the package.

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This loads an example image.

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This compares two different power spectrum calculations.

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The following shows the power spectrum calculated using Welch's method.

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