/// <summary>
/// Backward Fourier transform.
/// </summary>
/// <param name="data">Array</param>
private static void ifft(Complex32[] data)
{
int n = data.Length;
int m = Log2(n);
// reorder data first
FastFourierTransform.ReorderData(data);
// compute FFT
int tn = 1, tm, k, i, even, odd;
Complex32[] rotation;
Complex32 t, ce, co;
float tr, ti;
for (k = 1; k <= m; k++)
{
rotation = FastFourierTransform.BackwardComplexRotation(k);
tm = tn; tn <<= 1;
for (i = 0; i < tm; i++)
{
t = rotation[i];
for (even = i; even < n; even += tn)
{
odd = even + tm;
ce = data[even];
co = data[odd];
tr = co.Real * t.Real - co.Imag * t.Imag;
ti = co.Real * t.Imag + co.Imag * t.Real;
data[even].Real += tr;
data[even].Imag += ti;
data[odd].Real = ce.Real - tr;
data[odd].Imag = ce.Imag - ti;
}
}
}
}
/// <summary>
/// Initializes the fast Hilbert transform.
/// </summary>
/// <param name="normalized">Normalized transform or not</param>
/// <param name="direction">Processing direction</param>
public FastHilbertTransform(bool normalized = true, Direction direction = Direction.Vertical)
{
this.FFT = new FastFourierTransform(normalized, Direction.Both);
this.direction = direction;
}
/// <summary>
/// Initializes the fast Laplace transform.
/// </summary>
/// <param name="sigma">Standard deviation (0, 1)</param>
/// <param name="normalized">Normalized transform or not</param>
/// <param name="direction">Processing direction</param>
public FastLaplaceTransform(float sigma = 0.0005f, bool normalized = true, Direction direction = Direction.Vertical)
{
this.FFT = new FastFourierTransform(true, Direction.Vertical);
Sigma = sigma; this.normalized = normalized; this.direction = direction;
}
/// <summary>
/// Initializes the fast cosine transform.
/// </summary>
/// <param name="direction">Processing direction</param>
public FastCosineTransform(Direction direction = Direction.Vertical)
{
this.FFT = new FastFourierTransform(false, Direction.Both);
this.direction = direction;
}
/// <summary>
/// Initializes the fast Hartley transform.
/// </summary>
/// <param name="normalized">Normalized transform or not</param>
/// <param name="direction">Processing direction</param>
public FastHartleyTransform(bool normalized = true, Direction direction = Direction.Vertical)
{
this.FFT = new FastFourierTransform(normalized, direction);
}