Class FFT2D

Performs two dimensional FFT on a matrix of values. IMPORTANT: The matrix passed to this class for performing of 2D FFT need not necessarily have width equal to height but both width and height MUST be a power of two.

Inheritance
Object
FFT2D
Inherited Members
Namespace: AudioAnalysisTools.DSP
Assembly: AudioAnalysisTools.dll
Syntax
public class FFT2D

Methods

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FFT2Dimensional(Double[,])

Performs a 2D-Fourier transform on data in the passed Matrix/image.

Declaration
public static double[, ] FFT2Dimensional(double[, ] M)
Parameters
Type Name Description
Double[,] M
Returns
Type Description
Double[,]
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FFT2DOutput2MatrixOfMagnitude(Double[], Int32[])

First construct complex sampleData, then calculate the magnitude of sampleData.

Declaration
public static double[, ] FFT2DOutput2MatrixOfMagnitude(double[] sampleData, int[] dims)
Parameters
Type Name Description
Double[] sampleData
Int32[] dims
Returns
Type Description
Double[,]
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fftShift(Double[,])

This method "shifts" (that is, "rearranges") the quadrants of the magnitude matrix generated by the 2DFourierTransform such that the Top Left quadrant is swapped with the Bottom-Right quadrant and the Top-Right quadrant is swapped with the Bottom-Left. This has the effect of shifting the low frequency coefficients into the centre of the matrix and the high frequency coefficients are shifted to the edge of the image.

Declaration
public static double[, ] fftShift(double[, ] matrix)
Parameters
Type Name Description
Double[,] matrix
Returns
Type Description
Double[,]
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GetImageDataAsGrayIntensity(String, Boolean)

reads an image into a matrix. Takes weighted average of the RGB colours in each pixel.

Declaration
public static double[, ] GetImageDataAsGrayIntensity(string imageFilePath, bool reversed)
Parameters
Type Name Description
String imageFilePath
Boolean reversed
Returns
Type Description
Double[,]
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Matrix2ComplexVector(Double[,])

Concatenates the columns of the passed matrix and inserts zeros in every second position. The matrix is assumed to be an image and therefore read it using image coordinates. The output vector is now a vector of Complex numbers, with the imaginary part set to 0.

Declaration
public static Complex[] Matrix2ComplexVector(double[, ] M)
Parameters
Type Name Description
Double[,] M

The input matrix.
Returns
Type Description
Complex[]

A flattened M as a vactor.
Remarks

This method was created to replicate the functionality of Matrix2PaddedVector(Double[,]) to support a changed MathNet API.

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Matrix2PaddedVector(Double[,])

Concatenates the columns of the passed matrix and inserts zeros in every second position. The matrix is assumed to be an image and therefore read it using image coordinates. The output vector is now assumed to be a vector of Complex numbers, with the real values in the even positions and the imaginary numbers in the odd positions.

Declaration
public static double[] Matrix2PaddedVector(double[, ] M)
Parameters
Type Name Description
Double[,] M
Returns
Type Description
Double[]
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TestFFT2D()

METHOD to TEST the FFT2D.

Declaration
public static void TestFFT2D()

Extension Methods