/// <summary>
/// 1-D Fast Fourier Transform.
/// </summary>
///
/// <param name="real">The real part of the complex numbers to transform.</param>
/// <param name="imag">The imaginary part of the complex numbers to transform.</param>
/// <param name="direction">The transformation direction.</param>
///
/// <example>
/// <code source="Unit Tests\Accord.Tests.Math\FourierTransformTest.cs" region="doc_fft" />
/// </example>
///
public static void FFT(double[] real, double[] imag, FourierTransform.Direction direction)
{
if (direction == FourierTransform.Direction.Forward)
{
FFT(real, imag);
}
else
{
FFT(imag, real);
}
if (direction == FourierTransform.Direction.Backward)
{
for (int i = 0; i < real.Length; i++)
{
real[i] /= real.Length;
imag[i] /= real.Length;
}
}
}
/// <summary>
/// 1-D Fast Fourier Transform.
/// </summary>
///
/// <param name="data">The data to transform..</param>
/// <param name="direction">The transformation direction.</param>
///
public static void FFT(Complex[] data, FourierTransform.Direction direction)
{
int n = data.Length;
if (n == 0)
{
return;
}
if (direction == FourierTransform.Direction.Backward)
{
for (int i = 0; i < data.Length; i++)
{
data[i] = new Complex(data[i].Imaginary, data[i].Real);
}
}
if ((n & (n - 1)) == 0)
{
// Is power of 2
TransformRadix2(data);
}
else
{
// More complicated algorithm for arbitrary sizes
TransformBluestein(data);
}
if (direction == FourierTransform.Direction.Backward)
{
for (int i = 0; i < data.Length; i++)
{
double im = data[i].Imaginary;
double re = data[i].Real;
data[i] = new Complex(im / n, re / n);
}
}
}
public static object FHT(double[] Data, object BackwardFlagOpt)
{
bool backwards = Utils.GetOptionalParameter(BackwardFlagOpt, false);
FourierTransform.Direction direction = (backwards ? FourierTransform.Direction.Backward : FourierTransform.Direction.Forward);
try
{
HilbertTransform.FHT(Data, direction);
}
catch (Exception e)
{
Debug.WriteLine(e.ToString());
}
double[,] ret = new double[Data.Length, 1];
for (int i = 0; i < Data.Length; ++i)
{
ret[i, 0] = Data[i];
}
return(ret);
}
internal unsafe static Image <Complex, TDepth> FFT <TDepth>(this Image <Complex, TDepth> image, FourierTransform.Direction direction, bool inPlace = false)
where TDepth : struct
{
Image <Complex, TDepth> dest = null;
if (inPlace)
{
dest = image;
}
else
{
dest = image.Clone();
}
if (typeof(TDepth).Equals(typeof(float)))
{
FourierTransform.FFT2((ComplexF *)dest.ImageData, dest.Width, dest.Height, dest.Stride, direction);
}
else if (typeof(TDepth).Equals(typeof(double)))
{
throw new NotImplementedException(); //TODO: implement for double
//FourierTransform.FFT2((Complex*)dest.ImageData, dest.Width, dest.Height, dest.Stride, direction);
}
else
{
throw new NotSupportedException();
}
return(dest);
}
/// <summary>
/// Calculates Fast Fourier transform.
/// </summary>
/// <param name="image">Input image.</param>
/// <param name="direction">Forward or backward direction.</param>
/// <param name="inPlace">Process in place or not.</param>
/// <returns>Processed image. If <paramref name="inPlace"/> is used the result is the same as input image therefore may be omitted.</returns>
private unsafe static Image <Complex, double> FFT(this Image <Complex, double> image, FourierTransform.Direction direction, bool inPlace = false)
{
return(FFT <double>(image, direction, inPlace));
}
/// <summary>
/// Calculates Fast Fourier transform.
/// </summary>
/// <param name="image">Input image.</param>
/// <param name="direction">Forward or backward direction.</param>
/// <param name="inPlace">Process in place or not.</param>
/// <returns>Processed image. If <paramref name="inPlace"/> is used the result is the same as input image therefore may be omitted.</returns>
public unsafe static Image <Complex, float> FFT(this Image <Complex, float> image, FourierTransform.Direction direction, bool inPlace = false)
{
return(FFT <float>(image, direction, inPlace));
}
/// <summary>
/// 2-D Discrete Fourier Transform.
/// </summary>
///
/// <param name="data">The data to transform.</param>
/// <param name="direction">The transformation direction.</param>
///
/// <example>
/// <code source="Unit Tests\Accord.Tests.Math\FourierTransformTest.cs" region="doc_dft2" />
/// </example>
///
public static void DFT2(Complex[][] data, FourierTransform.Direction direction)
{
int m = data.Columns();
if (direction == FourierTransform.Direction.Forward)
{
// process rows
for (int i = 0; i < data.Length; i++)
{
// transform it
DFT(data[i], FourierTransform.Direction.Forward);
}
// process columns
var col = new Complex[data.Length];
for (int j = 0; j < m; j++)
{
// copy column
for (int i = 0; i < col.Length; i++)
{
col[i] = data[i][j];
}
// transform it
DFT(col, FourierTransform.Direction.Forward);
// copy back
for (int i = 0; i < col.Length; i++)
{
data[i][j] = col[i];
}
}
}
else
{
// process columns
var col = new Complex[data.Length];
for (int j = 0; j < m; j++)
{
// copy column
for (int i = 0; i < col.Length; i++)
{
col[i] = data[i][j];
}
// transform it
DFT(col, FourierTransform.Direction.Backward);
// copy back
for (int i = 0; i < col.Length; i++)
{
data[i][j] = col[i];
}
}
// process rows
for (int i = 0; i < data.Length; i++)
{
// transform it
DFT(data[i], FourierTransform.Direction.Backward);
}
}
}
