/// <summary>
/// Computes a 2-dimensional convolution filter for the provided sigma.
/// </summary>
/// <param name="stddev">Standard deviation of the Gaussian second derivative</param>
/// <param name="orientation">Orientation of the filter</param>
/// <returns>Convolution filter</returns>
public static float[,] ComputeFilter(float stddev, float orientation)
{
int halfsize = (int)Math.Ceiling(stddev * 7);
int size = halfsize * 2 + 1;
float center = size * .5f;
Gaussian gauss = new Gaussian(0, stddev * 3);
GaussianSecondDerivative sd = new GaussianSecondDerivative(0, stddev);
float[,] filter = new float[size, size];
float cos = (float)Math.Cos(orientation);
float sin = (float)Math.Sin(orientation);
for (int r = 0; r < size; r++)
{
for (int c = 0; c < size; c++)
{
float rTmp = r + .5f - center;
float cTmp = c + .5f - center;
float rr = sin * cTmp + cos * rTmp;
float cc = cos * cTmp - sin * rTmp;
float val1 = sd.Compute(rr);
float val2 = gauss.Compute(cc);
float value = val1 * val2;
filter[r, c] = value;
}
}
return(filter);
}
/// <summary>
/// Computes a 2-dimensional convolution filter for the provided sigma and point.
/// </summary>
/// <param name="column">Column of the point</param>
/// <param name="row">Row of the point</param>
/// <param name="size">Size of the patch</param>
/// <param name="stddev">Standard deviation of the Gaussian second derivative</param>
/// <returns>Convolution filter</returns>
public static float[,] ComputeFilter(int size, int row, int column, float stddev)
{
Gaussian gauss = new Gaussian(0, stddev);
float[,] filter = new float[size, size];
for (int r = 0; r < size; r++)
{
float dr = r + .5f - row;
for (int c = 0; c < size; c++)
{
float dc = c + .5f - column;
float distance = (float)Math.Sqrt(dr * dr + dc * dc);
float value = gauss.Compute(distance);
filter[r, c] = value;
}
}
return(filter);
}
/// <summary>
/// Computes a 2-dimensional convolution filter for the provided sigma.
/// </summary>
/// <param name="stddev">Standard deviation of the Gaussian second derivative</param>
/// <returns>Convolution filter</returns>
public static float[,] ComputeFilter(float stddev)
{
int halfsize = (int)Math.Ceiling(stddev * 3);
int size = halfsize * 2 + 1;
float center = size * .5f;
Gaussian gauss = new Gaussian(0, stddev);
float[,] filter = new float[size, size];
for (int r = 0; r < size; r++)
{
float dr = r + .5f - center;
for (int c = 0; c < size; c++)
{
float dc = c + .5f - center;
float distance = (float)Math.Sqrt(dr * dr + dc * dc);
float value = gauss.Compute(distance);
filter[r, c] = value;
}
}
return(filter);
}
