public DctComirva(int rows, int columns)
{
this.rows = rows;
this.columns = columns;
// Compute the DCT
// This whole section is copied from GetDCTMatrix() from CoMirva package
dctMatrix = new Matrix(rows, columns);
// Compute constants for DCT
// http://unix4lyfe.org/dct/
double k1 = Math.PI/columns;
double w1 = 1.0/(Math.Sqrt(columns));
double w2 = Math.Sqrt(2.0/columns);
// Generate 1D DCT-II matrix
for(int i = 0; i < rows; i++) {
for(int j = 0; j < columns; j++) {
if(i == 0)
dctMatrix.Set(i, j, w1 * Math.Cos(k1*i*(j + 0.5d)));
else
dctMatrix.Set(i, j, w2 * Math.Cos(k1*i*(j + 0.5d)));
}
}
}
/// <summary>
/// Generates the DCT matrix for the known number of filters (input vector) and
/// for the known number of used coefficients (output vector). Therfore the
/// DCT matrix has the dimensions (numberCoefficients x numberFilters).
/// If useFirstCoefficient is set to false the matrix dimensions are
/// (numberCoefficients-1 x numberFilters). This matrix is a submatrix of the
/// full matrix. Only the frist row is missing.
/// </summary>
/// <returns>Matrix the appropriate DCT matrix</returns>
public Matrix GetDCTMatrix()
{
//compute constants
double k = Math.PI/numberFilters;
double w1 = 1.0/(Math.Sqrt(numberFilters));
double w2 = Math.Sqrt(2.0/numberFilters);
//create new matrix
Matrix matrix = new Matrix(numberCoefficients, numberFilters);
//generate dct matrix
for(int i = 0; i < numberCoefficients; i++)
{
for(int j = 0; j < numberFilters; j++)
{
if(i == 0)
matrix.Set(i, j, w1 * Math.Cos(k*i*(j + 0.5d)));
else
matrix.Set(i, j, w2 * Math.Cos(k*i*(j + 0.5d)));
}
}
//adjust index if we are using first coefficient
if(!useFirstCoefficient)
matrix = matrix.GetMatrix(1, numberCoefficients-1, 0, numberFilters-1);
return matrix;
}