/// <summary>
/// Backward Walsh-Hadamard transform.
/// </summary>
/// <param name="B">Matrix</param>
/// <returns>Matrix</returns>
public Complex32[,] Backward(Complex32[,] B)
{
int N = B.GetLength(0), M = B.GetLength(1);
if (!Maths.IsPower(N, 2) || !Maths.IsPower(M, 2))
{
throw new Exception("Dimension of the signal must be a power of 2");
}
float[,] U = WalshHadamardTransform.Matrix((int)Maths.Log2(N));
float[,] V = WalshHadamardTransform.Matrix((int)Maths.Log2(M));
Complex32[,] A;
if (direction == Direction.Both)
{
A = U.Transponate().Dot(B).Dot(V);
A = normalized ? A.Div(Math.Sqrt(N * M)) : A;
}
else if (direction == Direction.Vertical)
{
A = U.Transponate().Dot(B);
A = normalized ? A.Div(Math.Sqrt(N)) : A;
}
else
{
A = B.Dot(V);
A = normalized ? A.Div(Math.Sqrt(M)) : A;
}
return(A);
}
/// <summary>
/// Forward Walsh-Hadamard transform.
/// </summary>
/// <param name="A">Matrix</param>
/// <returns>Matrix</returns>
public float[,] Forward(float[,] A)
{
int N = A.GetLength(0), M = A.GetLength(1);
if (!Maths.IsPower(N, 2) || !Maths.IsPower(M, 2))
{
throw new Exception("Dimension of the signal must be a power of 2");
}
float[,] U = WalshHadamardTransform.Matrix((int)Maths.Log2(N));
float[,] V = WalshHadamardTransform.Matrix((int)Maths.Log2(M));
float[,] B;
if (direction == Direction.Both)
{
B = U.Dot(A).Dot(V.Transponate());
B = normalized ? B.Div(Maths.Sqrt(N * M)) : B;
}
else if (direction == Direction.Vertical)
{
B = U.Dot(A);
B = normalized ? B.Div(Maths.Sqrt(N)) : B;
}
else
{
B = A.Dot(V.Transponate());
B = normalized ? B.Div(Maths.Sqrt(M)) : B;
}
return(B);
}
/// <summary>
/// Implements the construction of the Walsh-Hadamard matrix.
/// </summary>
/// <param name="powOf2">Power of 2</param>
/// <returns>Matrix</returns>
public static float[,] Matrix(int powOf2)
{
int iterations = powOf2 - 1;
float[,] hadamard = WalshHadamardTransform.Matrix();
if (iterations > 0)
{
float[,] H = WalshHadamardTransform.Matrix();
for (int i = 0; i < iterations; i++)
{
H = Matrice.Kronecker(H, hadamard);
}
return(H);
}
return(hadamard);
}
/// <summary>
/// Backward Walsh-Hadamard transform.
/// </summary>
/// <param name="B">Array</param>
/// <returns>Array</returns>
public Complex32[] Backward(Complex32[] B)
{
int N = B.Length;
if (!Maths.IsPower(N, 2))
{
throw new Exception("Dimension of the signal must be a power of 2");
}
int n = (int)Maths.Log2(N);
float[,] U = WalshHadamardTransform.Matrix(n);
Complex32[] A = Matrice.Dot(B, U.Transponate());
if (normalized)
{
A = Matrice.Div(A, Math.Sqrt(N));
}
return(A);
}
/// <summary>
/// Forward Walsh-Hadamard transform.
/// </summary>
/// <param name="A">Array</param>
/// <returns>Array</returns>
public Complex32[] Forward(Complex32[] A)
{
int N = A.Length;
if (!Maths.IsPower(N, 2))
{
throw new Exception("Dimension of the signal must be a power of 2");
}
int n = (int)Maths.Log2(N);
float[,] U = WalshHadamardTransform.Matrix(n);
Complex32[] B = Matrice.Dot(A, U);
if (normalized)
{
B = Matrice.Div(B, Math.Sqrt(N));
}
return(B);
}
