//
// Math.NET Numerics, part of the Math.NET Project
// http://numerics.mathdotnet.com
// http://github.com/mathnet/mathnet-numerics
//
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using System;
namespace IStation.Numerics.IntegralTransforms
{
///
/// Fast (FHT) Implementation of the Discrete Hartley Transform (DHT).
///
public static partial class Hartley
{
///
/// Naive forward DHT, useful e.g. to verify faster algorithms.
///
/// Time-space sample vector.
/// Hartley Transform Convention Options.
/// Corresponding frequency-space vector.
public static double[] NaiveForward(double[] timeSpace, HartleyOptions options)
{
var frequencySpace = Naive(timeSpace);
ForwardScaleByOptions(options, frequencySpace);
return frequencySpace;
}
///
/// Naive inverse DHT, useful e.g. to verify faster algorithms.
///
/// Frequency-space sample vector.
/// Hartley Transform Convention Options.
/// Corresponding time-space vector.
public static double[] NaiveInverse(double[] frequencySpace, HartleyOptions options)
{
var timeSpace = Naive(frequencySpace);
InverseScaleByOptions(options, timeSpace);
return timeSpace;
}
///
/// Rescale FFT-the resulting vector according to the provided convention options.
///
/// Fourier Transform Convention Options.
/// Sample Vector.
static void ForwardScaleByOptions(HartleyOptions options, double[] samples)
{
if ((options & HartleyOptions.NoScaling) == HartleyOptions.NoScaling ||
(options & HartleyOptions.AsymmetricScaling) == HartleyOptions.AsymmetricScaling)
{
return;
}
var scalingFactor = Math.Sqrt(1.0/samples.Length);
for (int i = 0; i < samples.Length; i++)
{
samples[i] *= scalingFactor;
}
}
///
/// Rescale the iFFT-resulting vector according to the provided convention options.
///
/// Fourier Transform Convention Options.
/// Sample Vector.
static void InverseScaleByOptions(HartleyOptions options, double[] samples)
{
if ((options & HartleyOptions.NoScaling) == HartleyOptions.NoScaling)
{
return;
}
var scalingFactor = 1.0/samples.Length;
if ((options & HartleyOptions.AsymmetricScaling) != HartleyOptions.AsymmetricScaling)
{
scalingFactor = Math.Sqrt(scalingFactor);
}
for (int i = 0; i < samples.Length; i++)
{
samples[i] *= scalingFactor;
}
}
}
}