/// <summary>
/// One dimensional Fast Fourier Transform.
/// </summary>
/// <param name="data">Data to transform.</param>
/// <param name="direction">Transformation direction.</param>
public unsafe static void FFT(ComplexF[] data, Direction direction)
{
fixed (ComplexF* dataPtr = data)
{
FFT(dataPtr, data.Length, direction);
}
}
/// <summary>
/// One dimensional Fast Fourier Transform.
/// </summary>
///
/// <param name="data">Data to transform.</param>
/// <param name="length">Array length.</param>
/// <param name="direction">Transformation direction.</param>
///
/// <remarks><para><note>The method accepts <paramref name="data"/> array of 2<sup>n</sup> size
/// only, where <b>n</b> may vary in the [1, 14] range.</note></para></remarks>
///
/// <exception cref="ArgumentException">Incorrect data length.</exception>
///
public unsafe static void FFT(ComplexF* data, int length, Direction direction)
{
int n = length;
int m = AForge.Math.Tools.Log2(n);
// reorder data first
ReorderData(data, length);
// compute FFT
int tn = 1, tm;
for (int k = 1; k <= m; k++)
{
ComplexF[] rotation = FourierTransform.GetComplexRotation(k, direction);
tm = tn;
tn <<= 1;
for (int i = 0; i < tm; i++)
{
ComplexF t = rotation[i];
for (int even = i; even < n; even += tn)
{
int odd = even + tm;
ComplexF* ce = &data[even];
ComplexF* co = &data[odd];
float tr = co->Re * t.Re - co->Im * t.Im;
float ti = co->Re * t.Im + co->Im * t.Re;
co->Re = ce->Re - tr;
co->Im = ce->Im - ti;
ce->Re += tr;
ce->Im += ti;
}
}
}
if (direction == Direction.Backward)
{
for (int i = 0; i < n; i++)
{
data[i].Re /= n;
data[i].Im /= n;
}
}
}
// Get rotation of complex number
private static ComplexF[] GetComplexRotation(int numberOfBits, Direction direction)
{
int directionIndex = (direction == Direction.Forward) ? 1 : 0;
// check if the array is already calculated
if (complexRotation[numberOfBits - 1, directionIndex] == null)
{
int n = 1 << (numberOfBits - 1);
float uR = 1.0f;
float uI = 0.0f;
double angle = System.Math.PI / n * (-(int)(direction));
float wR = (float)System.Math.Cos(angle);
float wI = (float)System.Math.Sin(angle);
float t;
ComplexF[] rotation = new ComplexF[n];
for (int i = 0; i < n; i++)
{
rotation[i] = new ComplexF { Re = uR, Im = uI};
t = uR * wI + uI * wR;
uR = uR * wR - uI * wI;
uI = t;
}
complexRotation[numberOfBits - 1, directionIndex] = rotation;
}
return complexRotation[numberOfBits - 1, directionIndex];
}
// Reorder data for FFT using
private unsafe static void ReorderData(ComplexF* data, int length)
{
int len = length;
// check data length
if ((len < minLength) || (len > maxLength) || (!AForge.Math.Tools.IsPowerOf2(len)))
throw new ArgumentException("Incorrect data length.");
int[] rBits = GetReversedBits(AForge.Math.Tools.Log2(len));
for (int i = 0; i < len; i++)
{
int s = rBits[i];
if (s > i)
{
ComplexF t = data[i];
data[i] = data[s];
data[s] = t;
}
}
}
/// <summary>
/// Two dimensional Fast Fourier Transform.
/// </summary>
/// <param name="data">Data to transform.</param>
/// <param name="direction">Transformation direction.</param>
public unsafe static void FFT2(ComplexF[,] data, Direction direction)
{
int width = data.GetLength(1);
int height = data.GetLength(0);
fixed (ComplexF* dataPtr = data)
{
FFT2(dataPtr, width, height, width, direction);
}
}
/// <summary>
/// Two dimensional Fast Fourier Transform.
/// </summary>
/// <param name="width">Image width.</param>
/// <param name="height">Image height.</param>
/// <param name="stride">Image stride.</param>
/// <param name="data">Data to transform.</param>
/// <param name="direction">Transformation direction.</param>
///
/// <remarks><para><note>The method accepts <paramref name="data"/> array of 2<sup>n</sup> size
/// only in each dimension, where <b>n</b> may vary in the [1, 14] range. For example, 16x16 array
/// is valid, but 15x15 is not.</note></para></remarks>
///
/// <exception cref="ArgumentException">Incorrect data length.</exception>
///
public unsafe static void FFT2(ComplexF* data, int width, int height, int stride, Direction direction)
{
int k = height;
int n = width;
// check data size
if (
(!AForge.Math.Tools.IsPowerOf2(k)) ||
(!AForge.Math.Tools.IsPowerOf2(n)) ||
(k < minLength) || (k > maxLength) ||
(n < minLength) || (n > maxLength)
)
{
throw new ArgumentException("Incorrect data length.");
}
// process rows
ComplexF* dataPtr = data; //get row
for (int i = 0; i < height; i++)
{
// transform it
FourierTransform.FFT(dataPtr, n, direction);
dataPtr += stride / sizeof(ComplexF);
}
// process columns
dataPtr = data; //get column
fixed (ComplexF* _col = new ComplexF[k])
{
ComplexF* col = _col;
for (int j = 0; j < height; j++)
{
// copy column
ComplexF* dataColPtr = &dataPtr[j];
for (int i = 0; i < k; i++)
{
col[i] = *dataColPtr;
dataColPtr += stride / sizeof(ComplexF);
}
// transform it
FourierTransform.FFT(col, k, direction);
// copy back
dataColPtr = &dataPtr[j];
for (int i = 0; i < k; i++)
{
*dataColPtr = col[i];
dataColPtr += stride / sizeof(ComplexF);
}
}
}
}
private static void mulComplex(ref ComplexF sourceA, ref ComplexF sourceB, ref ComplexF destination)
{
destination.Re = sourceA.Re * sourceB.Re;
destination.Im = sourceA.Im * sourceB.Im;
}
/// <summary>
/// Multiplies two complex images element-wise.
/// </summary>
/// <param name="imageA">First image.</param>
/// <param name="imageB">Second image.</param>
/// <param name="inPlace">
/// True to save the result in the first image, false otherwise.
/// <para>If true the returned image is the source image.</para>
/// </param>
/// <returns>Multiplied image.</returns>
public static ComplexF[,] MulComplex(this ComplexF[,] imageA, ComplexF[,] imageB, bool inPlace = false)
{
return imageA.Calculate(imageB, mulComplex, inPlace);
}
private static void convertGrayToComplex(Gray<float> source, ref ComplexF destination)
{
destination.Re = source.Intensity;
}
private static void convertComplexToMagnitude(ComplexF source, ref Gray<float> destination)
{
destination.Intensity = source.Magnitude();
}
/// <summary>
/// Two dimensional Fast Fourier Transform.
/// </summary>
/// <param name="width">Image width.</param>
/// <param name="height">Image height.</param>
/// <param name="stride">Image stride.</param>
/// <param name="data">Data to transform.</param>
/// <param name="direction">Transformation direction.</param>
///
/// <remarks><para><note>The method accepts <paramref name="data"/> array of 2<sup>n</sup> size
/// only in each dimension, where <b>n</b> may vary in the [1, 14] range. For example, 16x16 array
/// is valid, but 15x15 is not.</note></para></remarks>
///
/// <exception cref="ArgumentException">Incorrect data length.</exception>
///
public static unsafe void FFT2(ComplexF* data, int width, int height, int stride, Direction direction)
{
const int MIN_PATCH_SIZE = 32; //how much rows/columns should one thread process
int k = height;
int n = width;
// check data size
if (
(!AForge.Math.Tools.IsPowerOf2(k)) ||
(!AForge.Math.Tools.IsPowerOf2(n)) ||
(k < minLength) || (k > maxLength) ||
(n < minLength) || (n > maxLength)
)
{
throw new ArgumentException("Incorrect data length.");
}
// process rows
var procRow = new ParallelProcessor<bool, bool>(new Size(1 /*does not matter*/, height),
() => true,
(_, __, area) =>
{
ComplexF* dataPatchPtr = data + area.Y * stride / sizeof(ComplexF); //get row
for (int i = 0; i < area.Height; i++)
{
// transform it
FourierTransform.FFT(dataPatchPtr, n, direction);
dataPatchPtr += stride / sizeof(ComplexF);
}
},
new ParallelOptions2D { ParallelTrigger = (size) => size.Height >= MIN_PATCH_SIZE
/*,ForceSequential = true*/}
);
// process columns
//(y and x are swaped => proc thinks it is diving horizontal pacthes but instead we are using them as vertical ones)
var procCol = new ParallelProcessor<bool, bool>(new Size(1 /*does not matter*/, width),
() => true,
(_, __, area) =>
{
ComplexF* dataPatchPtr = &data[area.Y]; //get column
fixed (ComplexF* _col = new ComplexF[k])
{
ComplexF* col = _col;
for (int j = 0; j < area.Height; j++)
{
// copy column
ComplexF* dataColPtr = &dataPatchPtr[j];
for (int i = 0; i < k; i++)
{
col[i] = *dataColPtr;
dataColPtr += stride / sizeof(ComplexF);
}
// transform it
FourierTransform.FFT(col, k, direction);
// copy back
dataColPtr = &dataPatchPtr[j];
for (int i = 0; i < k; i++)
{
*dataColPtr = col[i];
dataColPtr += stride / sizeof(ComplexF);
}
}
}
},
new ParallelOptions2D { ParallelTrigger = (size) => size.Height >= MIN_PATCH_SIZE
/*,ForceSequential = true */}
);
procRow.Process(true);
procCol.Process(true);
}
