dct2D: Calculate and threshold DCT for an image

In ClaraHapp/MFPCA: Multivariate Functional Principal Component Analysis for Data Observed on Different Dimensional Domains

Description

This function calculates the (orthonormal) discrete cosine transformation for an image and returns thresholded DCT coefficients using the C-library fftw3 (see http://www.fftw.org/).

Usage

dct2D(image, qThresh)

Arguments

image	An image (a 2D matrix with real values).
qThresh	A numeric with value in [0,1], giving the quantile for thresholding the coefficients. See dctBasis2D for details.

Value

ind	An integer vector, containing the indices of non-thresholded (hence non-zero) coefficients.
val	A numeric vector, giving the values of the corresponding coefficients.

Warning

If the C-library fftw3 is not available when the package MFPCA is installed, this function is disabled an will throw an error. For full functionality install the C-library fftw3 from http://www.fftw.org/ and reinstall MFPCA. This function has not been tested with ATLAS/MKL/OpenBLAS.

See Also

dctBasis2D

ClaraHapp/MFPCA documentation built on Nov. 9, 2021, 11:35 p.m.